RYA Tactics
The perfect Tactical xmas present for your helm or crew
Personally signed by the author
RYA Tactics by Mark Rushall sheds a new light on the complexities of sailboat racing. No other sport requires the combination of so many elements – preparation, strategy, speed, tuning and most importantly tactics. However, it’s good tactics which can so often be that elusive missing skill.
As one of the sports top tacticians and coaches, and 2006 RYA Squad Coach of the Year, Mark’s book will help you sail better and improve your results. With easy to follow and logical diagrams, this book breaks new ground in presenting this essential and complex element of our sport.
“Covering almost every conceivable tactical situation, the book is a real tour de force by Rushall….yet comprises one of the easiest to read tactical situation books we have come across.” The Daily Sail, 1 May 07
“This book has come about from years of sailing and coaching at the highest level by an extremely analytical person. Mark …. is one of those annoying people who learnt from every sailing / coaching experience and has built an extensive memory bank of tactical scenarios and understanding.”
Chips Howarth, Fireball World Champion 2005
Tactics is the most comprehensive and accessible guide to racing yet. Providing an awesome and unique insight of sailboat tactics, it breaks down the race to tell you exactly what to think about, how and when to do it, and most importantly, why you should be doing it! No matter what your level of racing experience, you’ll have something to learn from Mark Rushall….”
Georgie Corlett, Editor, Dinghy Sailing Magazine
Start your 2008 season ready prepared and don’t go afloat without having read RYA Tactics.
Order your personally signed copy from www.rushall.net or for UK delivery send a cheque for £16 including P&P to:
Mark Rushall Tactics
Watermark Offices, 8 Lumley Gardens, Lumley Road, Emsworth, Hants, PO10 8AG, UK
International orders – please email tactics@rushall.net and postage rates will be advised.
Also available from www.rya.org.uk and most leading chandleries and book stores.
ENDS
Dinghy Sailing
On a Neilson dinghy sailing holiday, everyone is welcome, from complete beginners to enthusiastic improvers and accomplished experts looking for sunshine and the best conditions. Our approach to dinghy sailing tuition, and the type and quantity of equipment varies from club to club, ensuring that whatever your needs we have a holiday to suit your requirements perfectly.
Sailing means many things to different people. Some like to potter around over crystal clear waters while others crave the excitement of zooming across the waves on a high performance skiff.
Whatever your level of experience, the sense of freedom that comes from sailing is hard to beat. We offer the best boats, instructors and sailing areas together with free RYA training courses, enabling you to step aboard and take advantage of our 25 years of sailing experience.
Dinghy Sailing Tuition
National Sailing Scheme
We work closely with the RYA in developing the National Sailing Scheme. This progressive approach to tuition provides a tried-and-tested way to learn to sail. Holidays shouldn’t feel like school, so we endeavour to make everything from your first taster to high performance race techniques, as much fun as possible!
Start Sailing - Level 1
Great for those new to learn to sail holidays, Level 1 provides a comprehensive introduction to dinghy sailing. It is designed to get you on the water using modern, single-handed dinghies and requires no previous experience.
The course covers a wide variety of skills to enable you to sail confidently such as; wind awareness, rigging basics, knots and sailing theory.
Start Sailing is available in all of our centres.
Basic Skills - Level 2
Level 2 aims to fine-tune the skills and boat handling manoeuvres learnt at Level 1. The course sets out the foundations of sailing with the aim of producing competent light wind sailors who are able to sail and make informed decisions in good conditions.
You can expect to learn more advanced techniques in a variety of craft including; rigging according to weather conditions, coming alongside a moored boat, capsize recovery and essential safety background.
Try Finikounda – Great for the progressing beginner. Holiday sailing at it’s best!
Seamanship Skills
Moving on from Basic Skills, the main focus of this course is fine-tuning skills already learnt and boat handling manoeuvres, whilst increasing your self-reliance and decision making skills.
Day Sailing
We are able to endorse most sections of this course, enabling competent sailors to confidently plan and execute a safe day cruise, aspects covered include pilotage, interpretation of charts and use of GPS.
Finikounda is the main place to go for day sailing.
Sailing with Spinnakers
Sailing with Spinnakers teaches you how to sail a dinghy rigged with an asymmetric or symmetric spinnaker and some trapezing.
Try Porto Heli for a fantastic destination for a sailing holiday with tuition.
Start Racing
You will learn to race a variety of craft from single handers to performance boats. The aim is to gain a good understanding of the rules and techniques of racing, including the course and starting sequence, boat preparation, tactics and racing rules.
Performance Sailing
This is an advanced course for experienced sailors using high performance craft and covers a range of sessions including rigging, tuning, teamwork, trapezing, hiking, tacking and downwind sailing.
Porto Heli is the ideal place for performance sailing.
Dinghy Sailing Equipment
Advances in design and technology have continued to make dinghy sailing easier and more enjoyable than ever before. We've selected tghe best craft from leading British manufacturers Laser and RS, equipping our clubs with a range of kit to suit local wind and conditions.
Laser Funboats
Stable, safe and fun! Perfect for children. Available in all centres except Dahab
Laser Pico
A perfect beginners’ boat with easy-to-use controls. Available in all centres
Laser 1
The classic Olympic class single hander. Exciting sailing. Available in all centres except Vassiliki
Laser 2000
A popular boat for families and friends looking for a stable hull but no shortage of features.
Available in Halkidiki, Sivota, Ortakent, Finikounda and Porto Heli,
Laser 3000
A performance machine ideally suited to teenagers and lighter crews. Fast action with a spinnaker and trapeze. Available in Finikounda
Laser Bahia
A stable and spacious cockpit with space for up to 5 adults, together with a light hull and large gennaker makes a great day sail and cruising boat, with a performance edge.
Available in Lemnos and Lesvos
Laser 4000
Serious fun in the fast lane. A high performance skiff with adjustable racks and a large sail area. With tuition and practice, the 4000 flies. Available in Finikounda and Porto Heli
Laser Stratos
A good size family cruiser, the Stratos is ideal for day sailing, combining stability and performance features.Available in Lemnos, Lesvos, Halkidiki, Finikounda and Porto Heli
Laser Vago XD
Unmatched handling, versatility and exhilarating performance are harnessed by Laser in a unique modern design with high spec sails and trapeze. Available in Lemnos, Lesvos and Dahab
Dart 16
A popular catamaran equally at home pottering around on a day sail or on a trapezing joyride. The Dart 16 is a firm favourite in our centres. Available in all centres
Optimist
The definitive youth racer, the Optimist has traditionally been the first step on the road to success for competitive young sailors. Available in Porto Heli and Finikounda
RS Feva
A versatile dinghy, introducing several advanced features on a user friendly craft suited to younger sailors.Available in Finikounda, Porto Heli, Lemnos and Lesvos
RS 200
An easy to sail dinghy that brings the excitement of asymmetric sailing to everybody, including lighter sailors and youngsters. Available in Porto Heli
RS 400
LDC’s modern classic, a hiking asymmetric. The ultimate choice for the ambitious improver.
Available in Porto Heli
RS 500
Exciting performance with a simple user friendly layout and easy handling.Available in Porto Heli
RS 800
An exciting high performance skiff with twin trapeze that is remarkably easy for competent sailors to master.Available in Porto Heli and Finikounda
29er
A fast, exciting ride, the 29er is a high performance boat ideally suited to light weight sailors and youth racing.Available in Porto Heli
Children and Sailing Holidays
Hot Shots provides RYA tuition for 8-12 year olds whilst Starfish, Sea Urchins, Surfbusters and Sharksters provide fun for younger children and those less inclined to get out on the water.
Hot Shots
The water based activity club, for those that want it all: sailing, windsurfing, kayaking, snorkelling and plenty of sunshine, Hot Shots is the place to be.
Our fully qualified instructors help your youngsters master new skills and get first timers confident in no time at all. In-fact all our RYA qualified instructors will help your Hot Shots improve quickly, with the RYA Youth Sailing Awards, available to those who want to prove their skills.
When not out on the water, Hot Shots enjoy loads of land-based activities and making new friends has never been easier.
If your children are particularly interested in dinghy sailing, they will benefit from choosing a resort that specialises in that particular activity, such as Porto Heli
Hot Shots is open to all children ages 8-12 years and is available for a supplement of £80-£150 per week with the second week half price.
Where to go
Hot Shots is avilable in Lemnos, Finikounda, Vassiliki, Porto Heli and Dahab.
When not in our clubs, children under the age of 13 are welcome to windsurf with their parents. Children must be 13 years or over before they can join the adult windsurfing programme.
Flotilla Holidays
Flotilla Holidays - Another day. Another destination.
Explore hidden treasures every day; share your adventures in the evening with fellow sailors.
Life on flotilla is a holiday that just gets better every day.
Flotilla sailing holidays allow you to enjoy the independence of sailing your very own yacht from port to port during the day, but you also get to choose between pleasant evenings in the warm company of your fellow sailors, or spending them peacefully on your own deck.
On arrival
The Neilson Team will be there to greet you on arrival and show you to your yacht. Your lead crew will then join you on board to answer any questions you may have, show you where everything is and just check that everything is ship shape.
The remainder of the afternoon and evening is then yours to spend as you wish - enjoy a refreshing drink on deck, get to know some of your fellow sailors, explore the local area or stock up on any additional provisioning you require. You are then fully prepared for the start of your adventure the following day.
A day in the life…
As the morning sun peeps over your bow, your lead crew will join you for a chat about the day ahead, confirming the evening’s destination together with some great places to explore and idyllic lunch stops. Then as soon as everything’s ready, you’re free to slip your lines and set sail.
It’s entirely up to you and your crew how you reach your destination. You may want to race there before everybody else or meander there, anchoring for a lunch break and swim in a secluded bay. With the yacht to yourself, the day is yours to enjoy as you please. And if you wish to hook up with other parties on your flotilla they’re just a VHF radio call away - as is your lead crew, in case you need any help or advice.
As the afternoon drifts into evening and you glide into port, your lead crew will be waiting ashore to help you into your mooring, catch your lines and point out the location of shower facilities, bars and tavernas at your latest destination.
As the sun sets, you can settle in at one of the local tavernas, swapping stories with your fellow sailors over a bottle of wine and a hearty local meal. Of course, if all that sailing and sightseeing has taken it out of you, you can simply stay on your yacht and cook a meal in your own galley. That’s the beauty of flotilla holidays.
Your Yachting Experience
Our flotilla holidays in Greece and Croatia flotilla holidays require varying levels of confidence and experience due to the different routes and wind conditions in each area. It is important you select the right area for your party to ensure your safety and enjoyment.
The minimum experience we require on a flotilla holiday is that at least two people aboard each yacht are aged 18 years or over and must have had several day's active experience in charge of a yacht.
If this level of experience cannot be satisfied a Stay and Sail holiday, coupled with an Introduction to Yachting or Brush Up training course should be completed
Skippered Charter
If you want to regain your confidence afloat or just share the beginning of your flotilla with a like-minded sailor then you can pre book a member of the Neilson yacht team to join you on a skippered charter. They will spend the day with you, sailing from one place to another before retiring to the lead boat in the evening, allowing your party the privacy to enjoy some time alone. This option is available for one to three days for a supplement of £100 per yacht per day.
Please note, this option is not suitable for beginners who should complete an Introduction to Yachting course.
Bareboat Charter
Our Bareboat sailing holidays gives more experienced sailors the freedom to sail where, when and however they please. No itinerary, no set routes and no one to bother you. Bareboat holidays are the ultimate getaway.
Plot your own route around the many picturesque bays, lively little harbour towns and fishing villages scattered about the coastlines of our huge sailing areas. Spend as long as you like at any stop, return to your favourite places over and over, or keep on the move to discover something new around every point.
Of course, since you’re with Neilson you’ll still have the benefit of our expertise. Before you depart, our bareboat co-ordinator will go through the route you’ve planned, pointing out the highlights of your journey. And it’s always worth picking their brains, because they often have a nugget of advice that could really make your holiday. And naturally, they’ll also call or text you each morning to pass on weather conditions and check that everything on the yacht is as it should be.
All of our Bareboat holidays are provided with the following:
• Full tanks of diesel, water and gas
• Marine insurance
• Flights and transfers
• Comprehensive tools and spares
• A quick fix manual for everyday repair and maintenance
• Handheld GPS
• Additional charts and pilot book
• Mobile phone and charger
• Extra warps
• Starter pack
• No damage waiver or deposit to pay
Bareboat Holidays support Includes:
• A dedicated bareboat co-ordinator
• A full skipper and engineer’s briefing
• Details of all flotilla routes, staff and contact numbers
Experience Levels
When booking bareboat holidaywe ask that at least two people aboard are aged 18 years or over and have plenty of sailing knowledge and experience, having been in charge of a sailing vessel for several cruises, possibly on previous flotilla holidays. Both must be comfortable sailing in a range of conditions. If this level of experience cannot be satisfied, a flotilla holiday may be more appropriate.
Sail Training Courses
Yacht Training Courses
It’s not as hard as you might imagine to pick up the skills to navigate a yacht around the Mediterranean coastline. With our tried and tested courses and fantastic yacht trainers, you will be sailing with confidence in no time at all. We offer a number of courses to suit all ages and abilities.
Introduction to Yachting - four days
A course designed to be fun but informative, equipping complete beginners with the knowledge and skills necessary to skipper their own yacht on flotilla.
The syllabus we follow is based on the RYA Keelboat Level 2 certificate. After having completed the course, followed by a second week on flotilla, most new sailors will be awarded their RYA Level 2 certificate.
The skills needed can be learnt in four days with tuition from our Royal Yachting Association qualified instructors. Whilst covering the necessary manoeuvres you will be hopping from pontoon to quayside to bay to harbour. Occasionally stopping for picnics, taverna lunches or swimming, there will be time to digest all that you are learning at a relaxed but steady pace.
A maximum of five guests will train per yacht with an instructor.
At the end of your course you’ll feel confident and competent enough to skipper your own yacht within a flotilla environment. Your lead crew will be aware of your training and will be on hand to offer their full support during your week afloat.
Brush-Up Course - two days
Ideal for those with a basic or fading knowledge of sailing, or experienced dinghy sailors looking to make the step to big boat sailing. This course is tailored around your existing experience and looks to build your ability to sail confidently once more. You will spend two days with one of our RYA instructors who will assist you in practising and reviewing the skills you wish to improve.
The Brush-Up course can also be suitable for confident, advanced dinghy sailors who sail regularly at a high level. This course enables you to transfer your well-practised dinghy skills onto a larger class of boat. Beginner or intermediate dinghy sailors should book the Introduction to Yachting course.
Private Courses - Ideal for Families
Our Private Introduction to Yachting and Brush-Up courses are designed for groups or families who wish to learn together, on the same yacht, up to a maximum of five people. The course content is the same as detailed previously but you are guaranteed to be learning as one group without having to share your training yacht with another party.
The added advantage of a private course is that we can welcome 13 to 15 year olds aboard when accompanied by a parent. Younger sailors will relish the opportunity to learn with their family as a forerunner to the flotilla week of their holiday.
Private courses are priced per yacht at four times the cost of the individual course.
One Week Learn to Sail
If you can only get away on holiday for one week or spending two weeks learning to sail is not an option for you, then our One week Learn to Sail holiday is a perfect solution - half the week will be spent at one of our yacht bases living on your yacht whilst learning to sail on the Introduction to Yachting course. For the second part of the week, you will join your fellow sailors on flotilla.
Sailing Holidays
Sailing Holidays are great for those who like to remain active on their vacation.
Techniques
Here you will find articles on a variety of different sailing techniques
Plans to drop cats as a youth class
The RYA has recently made submissions to ISAF to remove the catamaran as a youth boat for 2009, and to remove the catamaran as an Olympic boat for 2012.
These submissions by the RYA were made without any consultation with the sailing community. We request that the submissions are withdrawn before the ISAF conference in early November and replaced by alternative submissions which support the use of catamarans both in future Olympics (2012 and beyond) and for youth training.
CATAMARANS OUT OF OLYMPICS
Amazingly the ISAF Council voted the Multihull out after the Events Committee had recommended that the cats stay in.
starter Boat for 7 year old
My sister wants to get her seven year old into sailing, the Oppi would seem to be the obvious choice but waht about some of the newer designs like Tera, Taz, Open etc ?
Dinghy Sailing in the Midlands
OK a bit cold this time of year
, but I am looking for ideaas for presents for my partner.
Sailing Holidays
Ok help required, girl friend just arrived home for pile of holiday brochures. Usual girlie things of lying on the beach. I really want to do a sailing holiday, try out some new boats etc, can anyone help with experiences of Sunsail type holidays ?
New to Dinghy Sailing
I am looking to start Dinghy Sailing in the new year, will I learn anything by going to the boat show ?, or are there any good sailing magazines to read ?
Catamaran Sailing
Is catamaran sailing better than dinghy sailing?
Yacht Charter
Although I love dinghy sailing, thought I would try some yachting. Some friends are looking at bareboat charter.
Laser 4.7, Radial or Laser Standard
Thinking about a new sailing dinghy after my Topper Lasers seem to be the most popular, but am I best with 4.7 or Radial, what about the Olympic one
Sailing in Spain
Where is the best place for sailing in Spain
BBC Sport Personality of Year
Very disappointing not to see any sailors or any sailing action covered on last night's awards. Plenty of successes this year
Sailing Videos
We have now included videos of sailing action, these can be found at
Winter Sailing Clothing
Gosh wasn't it cold this weekend, my hands were really frozen, any ideas of the best winter sailing gloves ?
NEW Boats for Sale and Gear For Sale Section
SailRacer now has a new For Sale section, here you will find 000s of items For Sale
You can advertsie for FREE, now is the time of year to clear out your garage of all those unused sailing items. There are sections for Boats, Sails, Gear, Clothing, Trailers and TrolleysLaser 4.7 World Championships
Any news from the Worlds ?
Why have the RYA decided to launch a race results
In the past, the RYA have asked clubs to send in their data at the end of every year. The data captured is limited and often open to subjectivity and goes through little validation by the RYA before being used in the statistical number crunching. After a very detailed review of the PYS by the RYA, it was highlighted that the data been captured by the RYA was become less and less meaningful, which was being reflected in the declining amount of returns being received by the RYA.
By launching the RYA Race results website, in collaboration with Simon Lovesey and SailRacer, the RYA are starting to increase the accuracy and meaningfulness of the data being collected by going straight to the source; individual race results. By asking clubs to upload their race results, the RYA are getting raw race data. The raw race data is also being subjected to an analysis in accordance with the RYA guidelines, which again increases the accuracy of the data being returned.
In summary, the RYA hope to collect more data, which is more meaningful to clubs as well as nationally, and start to increase the sailing publics confidence in the system and the numbers published by the RYA.
Benchmarking – why have I never heard of it befo
The term benchmarking is a new concept which the RYA have launched as part of the website initiative. However the overall concept has been instilled in the PYS pretty much since its conception over 50 years ago by using the term “yardstick”. Traditionally the advice given by the RYA was to find a known performer within a fleet of boats, a yardstick, against which other boats could be assessed to. The yardstick was very often a reliable boat and the RYA recommendations showed that clubs should ideally look to use either a Primary Yardstick or a Secondary Yardstick against which to carry out the fleet assessment.
However, as the number of types of boats increased and as the PYS branched out to cater for the Cruising side of club racing, some clubs were left without either a PY or SY to adjust against, or in some cases any boat that had a published number in the PN list.
To counter this the website has benefitted from a slight change in the system where instead of asking the club to pick a PY or SY for the assessment, it now looks known performers within the fleet. For example, a single Laser, whilst being a very stable PY, may not be the best boat to assess against as it is only one boat and as a single hander is open to wider performance changes. Therefore a club may wish to consider using an RS 400 for example, which as a SY would not be chosen under the old scheme. The website will also cater for those fleets without any boats published on the PN list as it will pick and recommend benchmarks to the club based on results. The club can always override the suggested benchmarks if it so chooses.
For more on the Benchmarking concept, please refer either to the Website Manual or contact the RYA Technical office.
Combining Classes
Hi,
Is there a easy way of combining two classes together.
For example:
"Laser" and "Laser Std" or "GP14" and "GP 14" or "RSFeva" and "RS Feva XL"
Regards
Ian
PS Keep up the good work on the new system. Definitely an improvement on the old system.
Problem with Race Dates
Using Sailwave, I've combined all the results from every series (some 40 races) and purged any duplicates, etc. and uploaded the file via Sailwave to the site.
When I try to import each race file I get the 'Enter Race Date' message. No matter what I try it gets rejected. The error messages shows any date either entered or chosen from the Calendar as 1/12/2010 for example 1-DEC-2009=1/12/2010.
I've tried to confuse the transformation by a date combination that might give me 12/1/2010 but with no success.
The dates of the races do not matter, but each race does need manual changes before benchmarking.
How do I get around this??
Barry McGibbon
Lyme Regis Sailing Club
Mods to Suggested Handicaps Page
Hi Simon,
Incorrect Data - GIGO ?
I was intending to import all the race results for our club. I loaded a few but it then occured to me that I may be doing something which is causing PYS to spit out odd handicap information. Our club sails in two fleets, slow and fast, but the results are held in a single Sailwave file. Sailwave formats out the results for the two fleets so that they appear nicely separated on our web site. The slow and fast fleets often sail different courses so there is no correlation between the times recorded for each fleet.
Does PYS treat all the boats in a race as sailing the same course or does it "notice" the fleet information and treat them, in our case, as two separate sets of results and calculate the corrected and on a fleet basis ?
Kerry Stares
{{redirect
Laser light
the song
LaserLight}} {{Other uses}} {{pp-semi-indef}} {{Use mdy dates
date=June 2012}} File:Military laser experiment.jpg
thumb
300px
right
United States Air Force laser experiment File:RGB laser.jpg
thumb
300px
right
Red (635 nm), green (532 nm), and blue-violet (445 nm) lasers A '''laser''' is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The term "laser" originated as an acronym for ''Light Amplification by Stimulated Emission of Radiation''.<ref name = "Gould1959"/><ref>{{cite web
accessdate=May 15, 2008
url=http://dictionary.reference.com/browse/laser
title=laser
publisher=Reference.com }}</ref> Lasers differ from other sources of light because they emit light coherence (physics)
coherently. Its spatial coherence allows a laser to be focused to a tight spot, and this enables applications like laser cutting and Photolithography#Light sources
laser lithography. Its spatial coherence also keeps a laser beam collimated light
collimated over long distances, and this enables laser pointers to work. Laser also have high temporal coherence which allows them to have a very narrow frequency spectrum
spectrum, i.e., they only emit a single color of light. Their temporal coherence also allows them to emit ultrashort pulse
pulses of light that only last a femtosecond. Lasers have many important applications. They are used in common consumer devices such as DVD players, laser printers, and barcode scanners. They are used in medicine for laser surgery and various skin treatments, and in industry for cutting and welding materials. They are used in military and law enforcement devices for marking targets and Laser_rangefinder#Military
measuring range and speed. Laser lighting displays use laser light as an entertainment medium. Lasers also have many important applications in scientific research. ==Fundamentals== Lasers are distinguished from other light sources by their coherence (physics)
coherence. Spatial coherence is typically expressed through the output being a narrow beam which is Gaussian beam
diffraction-limited, often a so-called "pencil beam." Laser beams can be focused to very tiny spots, achieving a very high irradiance, or they can be launched into beams of very low divergence in order to concentrate their power at a large distance. Temporal (or longitudinal) coherence implies a Polarization (waves)
polarized wave at a single frequency whose phase is correlated over a relatively large distance (the coherence length) along the beam.<ref>''Conceptual physics'', Paul Hewitt, 2002</ref> A beam produced by a thermal or other incoherent light source has an instantaneous amplitude and phase (waves)
phase which vary randomly with respect to time and position, and thus a very short coherence length. Most so-called "single wavelength" lasers actually produce radiation in several ''modes'' having slightly different frequencies (wavelengths), often not in a single polarization. And although temporal coherence implies monochromaticity, there are even lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously. There are some lasers which are not single spatial mode and consequently their light beams Beam divergence
diverge more than required by the diffraction limit. However all such devices are classified as "lasers" based on their method of producing that light: stimulated emission. Lasers are employed in applications where light of the required spatial or temporal coherence could not be produced using simpler technologies. ===Terminology=== File:Laser play.jpg
thumb
Laser beams in fog, reflected on a car windshield The word ''laser'' started as an acronym for "light amplification by stimulated emission of radiation"; in modern usage "light" broadly denotes electromagnetic radiation of any frequency, not only visible light, hence ''infrared laser'', ''ultraviolet laser'', ''X-ray laser'', and so on. Because the microwave predecessor of the laser, the maser, was developed first, devices of this sort operating at microwave and Radio frequency
radio frequencies are referred to as "masers" rather than "microwave lasers" or "radio lasers". In the early technical literature, especially at Bell Telephone Laboratories, the laser was called an '''optical maser'''; this term is now obsolete.<ref>{{cite web
title = Schawlow and Townes invent the laser
publisher = Lucent Technologies
year=1998
url = http://www.bell-labs.com/about/history/laser/
accessdate =October 24, 2006 }}</ref> A laser which produces light by itself is technically an optical oscillator rather than an optical amplifier as suggested by the acronym. It has been humorously noted that the acronym LOSER, for "light oscillation by stimulated emission of radiation," would have been more correct.<ref name="Biographical Memoirs">{{cite book
last=Chu
first=Steven
authorlink=Steven Chu
coauthors=Charles Hard Townes
Townes, Charles
editor=Edward P. Lazear (ed.),
title=Biographical Memoirs
year=2003
others=vol. 83
publisher=National Academy of Sciences
isbn=0-309-08699-X
page=202
chapter=Arthur Schawlow }}</ref> With the widespread use of the original acronym as a common noun, actual optical amplifiers have come to be referred to as "laser amplifiers", notwithstanding the apparent redundancy in that designation. The back-formation
back-formed verb ''to lase'' is frequently used in the field, meaning "to produce laser light,"<ref>{{cite web
url=http://dictionary.reference.com/browse/lase
title=lase
publisher=Dictionary.reference.com
accessdate=December 10, 2011}}</ref> especially in reference to the gain medium of a laser; when a laser is operating it is said to be "lasing." Further use of the words ''laser'' and ''maser'' in an extended sense, not referring to laser technology or devices, can be seen in usages such as ''astrophysical maser'' and ''atom laser''. ==Design== File:Laser.svg
thumb
Components of a typical laser:<br>1. Gain medium<br>2. Laser pumping energy<br>3. High reflector<br>4. Output coupler<br>5. Laser beam File:Laser, quantum principle.ogv
thumb
upright=1.5
animation explaining the stimulated emission and the Laser principle {{Main
Laser construction}} A laser consists of a Active laser medium
gain medium, a mechanism to supply energy to it, and something to provide optical feedback.<ref>{{cite book
first = Anthony E.
last=Siegman
year=1986
title=Lasers
publisher=University Science Books
isbn= 0-935702-11-3
page=2}}</ref> The gain medium is a material with properties that allow it to optical amplifier
amplify light by stimulated emission. Light of a specific wavelength that passes through the gain medium is amplified (increases in power). For the gain medium to amplify light, it needs to be supplied with energy. This process is called laser pumping
pumping. The energy is typically supplied as an electrical current, or as light at a different wavelength. Pump light may be provided by a Xenon flash lamp
flash lamp or by another laser. The most common type of laser uses feedback from an optical cavity—a pair of mirrors on either end of the gain medium. Light bounces back and forth between the mirrors, passing through the gain medium and being amplified each time. Typically one of the two mirrors, the output coupler, is partially transparent. Some of the light escapes through this mirror. Depending on the design of the cavity (whether the mirrors are flat or curved mirror
curved), the light coming out of the laser may spread out or form a narrow light beam
beam. This type of device is sometimes called a ''laser oscillator'' in analogy to electronic oscillators, in which an electronic amplifier receives electrical feedback that causes it to produce a signal. Most practical lasers contain additional elements that affect properties of the emitted light such as the polarization, the wavelength, and the shape of the beam. ==Laser physics== {{See also
Laser science}} Electrons and how they interact with electromagnetic fields are important in our understanding of chemistry and physics. === Stimulated emission === In the Classical electromagnetism
classical view, the energy of an electron orbiting an atomic nucleus is larger for orbits further from the atomic nucleus
nucleus of an atom. However, quantum mechanical effects force electrons to take on discrete positions in Atomic orbital
orbitals. Thus, electrons are found in specific energy levels of an atom, two of which are shown below: File:Stimulated Emission.svg
center
550px When an electron absorbs energy either from light (photons) or heat (phonons), it receives that incident quantum of energy. But transitions are only allowed in between discrete energy levels such as the two shown above. This leads to emission lines and Spectral line
absorption lines. When an electron is Excited state
excited from a lower to a higher energy level, it will not stay that way forever. An electron in an excited state may decay to a lower energy state which is not occupied, according to a particular time constant characterizing that transition. When such an electron decays without external influence, emitting a photon, that is called "spontaneous emission". The phase associated with the photon that is emitted is random. A material with many atoms in such an excited state may thus result in radiation which is very spectrally limited (centered around one wavelength of light), but the individual photons would have no common phase relationship and would emanate in random directions. This is the mechanism of fluorescence and thermal emission. An external electromagnetic field at a frequency associated with a transition can affect the quantum mechanical state of the atom. As the electron in the atom makes a transition between two stationary states (neither of which shows a dipole field), it enters a transition state which does have a dipole field, and which acts like a small electric dipole, and this dipole oscillates at a characteristic frequency. In response to the external electric field at this frequency, the probability of the atom entering this transition state is greatly increased. Thus, the rate of transitions between two stationary states is enhanced beyond that due to spontaneous emission. Such a transition to the higher state is called Absorption (electromagnetic radiation)
absorption, and it destroys an incident photon (the photon's energy goes into powering the increased energy of the higher state). A transition from the higher to a lower energy state, however, produces an additional photon; this is the process of '''stimulated emission'''. === Gain medium and cavity === File:Laser DSC09088.JPG
thumb
300px
A helium-neon laser demonstration at the Kastler-Brossel Laboratory at Paris VI
Univ. Paris 6. The pink-orange glow running through the center of the tube is from the electric discharge which produces incoherent light, just as in a neon tube. This glowing plasma is excited and then acts as the active laser medium
gain medium through which the internal beam passes, as it is reflected between the two mirrors. Laser radiation output through the front mirror can be seen to produce a tiny (about 1mm in diameter) intense spot on the screen, to the right. Although it is a deep and pure red color, spots of laser light are so intense that cameras are typically overexposed and distort their color. File:Helium neon laser spectrum.svg
thumb
Spectrum of a helium neon laser illustrating its very high spectral purity (limited by the measuring apparatus). The .002 nm bandwidth of the lasing medium is well over 10,000 times narrower than the spectral width of a light-emitting diode (whose spectrum is shown ''':Image:Red-YellowGreen-Blue LED spectra.png
here''' for comparison), with the bandwidth of a single longitudinal mode being much narrower still. The gain medium is excited by an external source of energy into an excited state. In most lasers this medium consists of population of atoms which have been excited into such a state by means of an outside light source, or an electrical field which supplies energy for atoms to absorb and be transformed into their excited states. The gain medium of a laser is normally a material of controlled purity, size, concentration, and shape, which amplifies the beam by the process of stimulated emission described above. This material can be of any state of matter
state: gas, liquid, solid, or plasma (physics)
plasma. The gain medium absorbs pump energy, which raises some electrons into higher-energy ("excited state
excited") quantum states. Particles can interact with light by either absorbing or emitting photons. Emission can be spontaneous or stimulated. In the latter case, the photon is emitted in the same direction as the light that is passing by. When the number of particles in one excited state exceeds the number of particles in some lower-energy state, population inversion is achieved and the amount of stimulated emission due to light that passes through is larger than the amount of absorption. Hence, the light is amplified. By itself, this makes an optical amplifier. When an optical amplifier is placed inside a resonant optical cavity, one obtains a laser oscillator.<ref>{{cite book
first = Anthony E.
last=Siegman
year=1986
title=Lasers
publisher=University Science Books
isbn= 0-935702-11-3
page=4}}</ref> In a few situations it is possible to obtain lasing with only a single pass of EM radiation through the gain medium, and this produces a laser beam without any need for a resonant or reflective cavity (see for example nitrogen laser).<ref name="Light and Its Uses, Nitrogen Laser" >{{Cite book
title=Light and Its Uses
chapter=Nitrogen Laser
publisher=Scientific American
date=June 1974
isbn=0-7167-1185-0
pages=40–43
ref=Light and Its Uses }}</ref> Thus, reflection in a resonant cavity is usually required for a laser, but is not absolutely necessary. The optical resonator is sometimes referred to as an "optical cavity", but this is a misnomer: lasers use open resonators as opposed to the literal cavity that would be employed at microwave frequencies in a maser. The resonator typically consists of two mirrors between which a coherent beam of light travels in both directions, reflecting back on itself so that an average photon will pass through the gain medium repeatedly before it is emitted from the output aperture or lost to diffraction or absorption. If the gain (amplification) in the medium is larger than the resonator losses, then the power of the recirculating light can rise exponential growth
exponentially. But each stimulated emission event returns an atom from its excited state to the ground state, reducing the gain of the medium. With increasing beam power the net gain (gain minus loss) reduces to unity and the gain medium is said to be saturated. In a continuous wave (CW) laser, the balance of pump power against gain saturation and cavity losses produces an equilibrium value of the laser power inside the cavity; this equilibrium determines the operating point of the laser. If the applied pump power is too small, the gain will never be sufficient to overcome the resonator losses, and laser light will not be produced. The minimum pump power needed to begin laser action is called the ''lasing threshold''. The gain medium will amplify any photons passing through it, regardless of direction; but only the photons in a spatial mode supported by the resonator will pass more than once through the medium and receive substantial amplification. === The light emitted === The light generated by stimulated emission is very similar to the input signal in terms of wavelength, phase (waves)
phase, and polarization. This gives laser light its characteristic coherence, and allows it to maintain the uniform polarization and often monochromaticity established by the optical cavity design. The beam in the cavity and the output beam of the laser, when travelling in free space (or a homogenous medium) rather than waveguides (as in an optical fiber laser), can be approximated as a Gaussian beam in most lasers; such beams exhibit the minimum divergence for a given diameter. However some high power lasers may be multimode, with the transverse modes often approximated using Hermite polynomials
Hermite-Gaussian function
Gaussian or Laguerre polynomials
Laguerre-Gaussian functions. It has been shown that unstable laser resonators (not used in most lasers) produce fractal shaped beams.<ref>G. P. Karman, G. S. McDonald, G. H. C. New, J. P. Woerdman, "[http://www.nature.com/nature/journal/v402/n6758/abs/402138a0.html Laser Optics: Fractal modes in unstable resonators]", ''Nature'', Vol. 402, 138, November 11, 1999.</ref> Near the beam "waist" (or focus (optics)
focal region) it is highly ''collimated light
collimated'': the wavefronts are planar, normal to the direction of propagation, with no beam divergence at that point. However due to diffraction, that can only remain true well within the Rayleigh range. The beam of a single transverse mode (gaussian beam) laser eventually diverges at an angle which varies inversely with the beam diameter, as required by diffraction theory. Thus, the "pencil beam" directly generated by a common helium-neon laser would spread out to a size of perhaps 500 kilometers when shone on the Moon (from the distance of the earth). On the other hand the light from a semiconductor laser typically exits the tiny crystal with a large divergence: up to 50°. However even such a divergent beam can be transformed into a similarly collimated beam by means of a lens (optics)
lens system, as is always included, for instance, in a laser pointer whose light originates from a laser diode. That is possible due to the light being of a single spatial mode. This unique property of laser light, Coherence (physics)#Spatial coherence
spatial coherence, cannot be replicated using standard light sources (except by discarding most of the light) as can be appreciated by comparing the beam from a flashlight (torch) or spotlight to that of almost any laser. === Quantum vs. classical emission processes === The mechanism of producing radiation in a laser relies on stimulated emission, where energy is extracted from a transition in an atom or molecule. This is a quantum phenomenon discovered by Einstein who derived the relationship between the Spontaneous emission#Rate of spontaneous emission
A coefficient describing spontaneous emission and the Stimulated emission#Mathematical model
B coefficient which applies to absorption and stimulated emission. However in the case of the free electron laser, atomic energy levels are not involved; it appears that the operation of this rather exotic device can be explained without reference to quantum mechanics. ==Continuous and pulsed modes of operation== A laser can be classified as operating in either continuous or pulsed mode, depending on whether the power output is essentially continuous over time or whether its output takes the form of pulses of light on one or another time scale. Of course even a laser whose output is normally continuous can be intentionally turned on and off at some rate in order to create pulses of light. When the modulation rate is on time scales much slower than the Q factor#Optical systems
cavity lifetime and the time period over which energy can be stored in the lasing medium or pumping mechanism, then it is still classified as a "modulated" or "pulsed" continuous wave laser. Most laser diodes used in communication systems fall in that category. ===Continuous wave operation=== Some applications of lasers depend on a beam whose output power is constant over time. Such a laser is known as ''continuous wave'' (''CW''). Many types of lasers can be made to operate in continuous wave mode to satisfy such an application. Many of these lasers actually lase in several longitudinal modes at the same time, and beats between the slightly different optical frequencies of those oscillations will in fact produce amplitude variations on time scales shorter than the round-trip time (the reciprocal of the Free spectral range#Fabry–Pérot interferometer
frequency spacing between modes), typically a few nanoseconds or less. In most cases these lasers are still termed "continuous wave" as their output power is steady when averaged over any longer time periods, with the very high frequency power variations having little or no impact in the intended application. (However the term is not applied to Mode-locking
mode-locked lasers, where the ''intention'' is to create very short pulses at the rate of the round-trip time). For continuous wave operation it is required for the population inversion of the gain medium to be continually replenished by a steady pump source. In some lasing media this is impossible. In some other lasers it would require pumping the laser at a very high continuous power level which would be impractical or destroy the laser by producing excessive heat. Such lasers cannot be run in CW mode. ===Pulsed operation=== Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. This encompasses a wide range of technologies addressing a number of different motivations. Some lasers are pulsed simply because they cannot be run in #Continuous wave operation
continuous mode. In other cases the application requires the production of pulses having as large an energy as possible. Since the pulse energy is equal to the average power divided by the repetition rate, this goal can sometimes be satisfied by lowering the rate of pulses so that more energy can be built up in between pulses. In laser ablation for example, a small volume of material at the surface of a work piece can be evaporated if it is heated in a very short time, whereas supplying the energy gradually would allow for the heat to be absorbed into the bulk of the piece, never attaining a sufficiently high temperature at a particular point. Other applications rely on the peak pulse power (rather than the energy in the pulse), especially in order to obtain nonlinear optical effects. For a given pulse energy, this requires creating pulses of the shortest possible duration utilizing techniques such as Q-switching. The optical bandwidth of a pulse cannot be narrower than the reciprocal of the pulse width. In the case of extremely short pulses, that implies lasing over a considerable bandwidth, quite contrary to the very narrow bandwidths typical of CW lasers. The lasing medium in some ''dye lasers'' and ''vibronic solid-state lasers'' produces optical gain over a wide bandwidth, making a laser possible which can thus generate pulses of light as short as a few femtoseconds (10<sup>-15</sup> s). ====Q-switching==== {{Main
Q-switching}} In a Q-switched laser, the population inversion is allowed to build up by introducing loss inside the resonator which exceeds the gain of the medium; this can also be described as a reduction of the quality factor or 'Q' of the cavity. Then, after the pump energy stored in the laser medium has approached the maximum possible level, the introduced loss mechanism (often an electro- or acousto-optical element) is rapidly removed (or that occurs by itself in a passive device), allowing lasing to begin which rapidly obtains the stored energy in the gain medium. This results in a short pulse incorporating that energy, and thus a high peak power. ====Mode-locking==== {{Main
Mode-locking}} A mode-locked laser is capable of emitting extremely short pulses on the order of tens of picoseconds down to less than 10 femtoseconds. These pulses will repeat at the round trip time, that is, the time that it takes light to complete one round trip between the mirrors comprising the resonator. Due to the Fourier uncertainty principle
Fourier limit (also known as energy-time Uncertainty principle
uncertainty), a pulse of such short temporal length has a spectrum spread over a considerable bandwidth. Thus such a gain medium must have a gain bandwidth sufficiently broad to amplify those frequencies. An example of a suitable material is titanium-doped, artificially grown sapphire (Ti-sapphire laser
Ti:sapphire) which has a very wide gain bandwidth and can thus produce pulses of only a few femtoseconds duration. Such mode-locked lasers are a most versatile tool for researching processes occurring on extremely short time scales (known as femtosecond physics, femtosecond chemistry and ultrafast science), for maximizing the effect of nonlinear optics
nonlinearity in optical materials (e.g. in second-harmonic generation, parametric down-conversion, optical parametric oscillators and the like) due to the large peak power, and in ablation applications.{{Citation needed
date=November 2010}} Again, because of the extremely short pulse duration, such a laser will produce pulses which achieve an extremely high peak power. ====Pulsed pumping==== Another method of achieving pulsed laser operation is to pump the laser material with a source that is itself pulsed, either through electronic charging in the case of flash lamps, or another laser which is already pulsed. Pulsed pumping was historically used with dye lasers where the inverted population lifetime of a dye molecule was so short that a high energy, fast pump was needed. The way to overcome this problem was to charge up large capacitors which are then switched to discharge through flashlamps, producing an intense flash. Pulsed pumping is also required for three-level lasers in which the lower energy level rapidly becomes highly populated preventing further lasing until those atoms relax to the ground state. These lasers, such as the excimer laser and the copper vapor laser, can never be operated in CW mode. ==History== ===Foundations=== In 1917, Albert Einstein established the theoretical foundations for the laser and the maser in the paper ''Zur Quantentheorie der Strahlung'' (On the Quantum Theory of Radiation); via a re-derivation of Max Planck's law of radiation, conceptually based upon probability coefficients (Einstein coefficients) for the absorption, spontaneous emission, and stimulated emission of electromagnetic radiation; in 1928, Rudolf W. Ladenburg confirmed the existences of the phenomena of stimulated emission and negative absorption;<ref name="Steen, W. M 1998">Steen, W. M. "Laser Materials Processing", 2nd Ed. 1998.</ref> in 1939, Valentin A. Fabrikant predicted the use of stimulated emission to amplify "short" waves;<ref>{{it icon}} {{cite web
url=http://wwwold.unimib.it/ateneo/presentazione/direzione_ammva/prevenzione_protezione/Semin_sicur_laser.ppt
title=Il rischio da laser: cosa č e come affrontarlo; analisi di un problema non cosě lontano da noi ("The risk from laser: what it is and what it is like facing it; analysis of a problem which is thus mot far away from us."), Programma Corso di Formazione Obbligatorio anno 2004, Dimitri Batani (Powerpoint presentation >7Mb)
accessdate=January 1, 2007
publisher=wwwold.unimib.it}}</ref> in 1947, Willis E. Lamb and R. C. Retherford found apparent stimulated emission in hydrogen spectra and effected the first demonstration of stimulated emission;<ref name="Steen, W. M 1998"/> in 1950, Alfred Kastler (Nobel Prize for Physics 1966) proposed the method of optical pumping, experimentally confirmed, two years later, by Brossel, Kastler, and Winter.<ref>[http://nobelprize.org/nobel_prizes/physics/laureates/1966/press.html The Nobel Prize in Physics 1966] Presentation Speech by Professor Ivar Waller. Retrieved January 1, 2007.</ref> ===Maser=== {{Main
Maser}} File:Aleksandr Prokhorov.jpg
upright
thumb
right
Aleksandr Prokhorov In 1953, Charles Hard Townes and graduate students James P. Gordon and Herbert J. Zeiger produced the first microwave amplifier, a device operating on similar principles to the laser, but amplifying microwave radiation rather than infrared or visible radiation. Townes's maser was incapable of continuous output.{{Citation needed
date=November 2010}} Meanwhile, in the Soviet Union, Nikolay Basov and Aleksandr Mikhailovich Prokhorov
Aleksandr Prokhorov were independently working on the quantum oscillation
oscillator and solved the problem of continuous-output systems by using more than two energy levels. These gain media could release stimulated emissions between an excited state and a lower excited state, not the ground state, facilitating the maintenance of a population inversion. In 1955, Prokhorov and Basov suggested optical pumping of a multi-level system as a method for obtaining the population inversion, later a main method of laser pumping. Townes reports that several eminent physicists – among them Niels Bohr, John von Neumann, Isidor Rabi, Polykarp Kusch, and Llewellyn Thomas — argued the maser violated Heisenberg's uncertainty principle and hence could not work.<ref>Townes, Charles H. (1999). [http://books.google.com/books?id=VrbD41GGeJYC&pg=PA69&lpg=PA69&dq=%22niels+bohr%22+rabi+kusch+von+neumann+laser&source=web&ots=0_A7OuramT&sig=4R4yTmk6SmJTN8mZaiOMzgg-LO4 ''How the Laser Happened: Adventures of a Scientist'']. Oxford University Press. pp. 69-70. Archived at Google Books.</ref> In 1964 Charles H. Townes, Nikolay Basov, and Aleksandr Prokhorov shared the Nobel Prize in Physics, "for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser–laser principle". ===Laser===<!--WP:MOSHEAD notwithstanding--> In 1957, Charles Hard Townes and Arthur Leonard Schawlow, then at Bell Labs, began a serious study of the infrared laser. As ideas developed, they abandoned infrared radiation to instead concentrate upon visible light. The concept originally was called an "optical maser". In 1958, Bell Labs filed a patent application for their proposed optical maser; and Schawlow and Townes submitted a manuscript of their theoretical calculations to the ''Physical Review'', published that year in Volume 112, Issue No. 6. File:Gould notebook 001.jpg
thumb
right
'''LASER notebook:''' First page of the notebook wherein Gordon Gould coined the LASER acronym, and described the technology
technologic elements for constructing the device.<!--FAIR USE of Gould notebook 001.jpg: see image description page at Image:Gould notebook 001.jpg for rationale --> Simultaneously, at Columbia University, graduate student Gordon Gould was working on a doctoral thesis about the energy levels of excited thallium. When Gould and Townes met, they spoke of radiation Emission (electromagnetic radiation)
emission, as a general subject; afterwards, in November 1957, Gould noted his ideas for a "laser", including using an open resonator (later an essential laser-device component). Moreover, in 1958, Prokhorov independently proposed using an open resonator, the first published appearance (the USSR) of this idea. Elsewhere, in the U.S., Schawlow and Townes had agreed to an open-resonator laser design – apparently unaware of Prokhorov's publications and Gould's unpublished laser work. At a conference in 1959, Gordon Gould published the term LASER in the paper ''The LASER, Light Amplification by Stimulated Emission of Radiation''.<ref name="Gould1959">{{cite book
last=Gould
first= R. Gordon
authorlink=Gordon Gould
year=1959
chapter=The LASER, Light Amplification by Stimulated Emission of Radiation
editor= Franken, P.A. and Sands, R.H. (Eds.)
title = The Ann Arbor Conference on Optical Pumping, the University of Michigan, 15 June through 18 June 1959
page=128
oclc=02460155}}</ref><ref name="Biographical Memoirs"/> Gould's linguistic intention was using the "-aser" word particle as a suffix – to accurately denote the spectrum of the light emitted by the LASER device; thus x-rays: ''xaser'', ultraviolet: ''uvaser'', et cetera; none established itself as a discrete term, although "raser" was briefly popular for denoting radio-frequency-emitting devices. Gould's notes included possible applications for a laser, such as Spectroscopy
spectrometry, interferometry, radar, and nuclear fusion. He continued developing the idea, and filed a patent application in April 1959. The United States Patent and Trademark Office
U.S. Patent Office denied his application, and awarded a patent to Bell Labs, in 1960. That provoked a twenty-eight-year lawsuit, featuring scientific prestige and money as the stakes. Gould won his first minor patent in 1977, yet it was not until 1987 that he won the first significant patent lawsuit victory, when a Federal judge ordered the U.S. Patent Office to issue patents to Gould for the optically pumped and the gas discharge laser devices. The question of just how to assign credit for inventing the laser remains unresolved by historians.<ref>Joan Lisa Bromberg, ''The Laser in America, 1950–1970'' (1991), pp. 74–77 [http://www.aip.org/history/exhibits/laser/sections/whoinvented.html online]</ref> On May 16, 1960, Theodore Maiman
Theodore H. Maiman operated the first functioning laser,<ref>{{cite journal
last=Maiman
first=T. H.
authorlink=Theodore Harold Maiman
year=1960
title=Stimulated optical radiation in ruby
journal=Nature
volume=187
issue=4736
pages=493–494
doi=10.1038/187493a0
bibcode = 1960Natur.187..493M }}</ref><ref>{{cite web
accessdate=May 15, 2008
url=http://www.press.uchicago.edu/Misc/Chicago/284158_townes.html
title=The first laser
publisher=University of Chicago
author=Charles Hard Townes
Townes, Charles Hard }}</ref> at Hughes Research Laboratories, Malibu, California, ahead of several research teams, including those of Charles H. Townes
Townes, at Columbia University, Arthur L. Schawlow
Arthur Schawlow, at Bell Labs,<ref>{{cite book
last=Hecht
first=Jeff
year=2005
title=Beam: The Race to Make the Laser
publisher=Oxford University Press
isbn=0-19-514210-1}}</ref> and Gould, at the TRG (Technical Research Group) company. Maiman's functional laser used a solid-state flashlamp-pumped synthetic ruby crystal to produce red laser light, at 694 nanometres wavelength; however, the device only was capable of pulsed operation, because of its three-level pumping design scheme. Later in 1960, the Iranian physicist Ali Javan, and William R. Bennett, Jr.
William R. Bennett, and Donald R. Herriott
Donald Herriott, constructed the first gas laser, using helium and neon that was capable of continuous operation in the infrared (U.S. Patent 3,149,290); later, Javan received the Albert Einstein Award in 1993. Basov and Javan proposed the semiconductor laser diode concept. In 1962, Robert N. Hall demonstrated the first ''laser diode'' device, made of gallium arsenide and emitted at 850 nm the near-infrared band of the spectrum. Later, in 1962, Nick Holonyak
Nick Holonyak, Jr. demonstrated the first semiconductor laser with a visible emission. This first semiconductor laser could only be used in pulsed-beam operation, and when cooled to liquid nitrogen temperatures (77 K). In 1970, Zhores Ivanovich Alferov
Zhores Alferov, in the USSR, and Izuo Hayashi and Morton Panish of Bell Telephone Laboratories also independently developed room-temperature, continual-operation diode lasers, using the heterojunction structure. === Recent innovations === File:History of laser intensity.svg
thumb
250px
Graph showing the history of maximum laser pulse intensity throughout the past 40 years. Since the early period of laser history, laser research has produced a variety of improved and specialized laser types, optimized for different performance goals, including: * new wavelength bands * maximum average output power * maximum peak pulse energy * maximum peak pulse power (physics)
power * minimum output pulse duration * maximum power efficiency * minimum cost and this research continues to this day. Lasing without maintaining the medium excited into a population inversion {{dubious
date=November 2010}} was discovered in 1992 in sodium gas and again in 1995 in rubidium gas by various international teams.{{Citation needed
date=November 2010}} This was accomplished by using an external maser to induce "optical transparency" in the medium by introducing and destructively interfering the ground electron transitions between two paths, so that the likelihood for the ground electrons to absorb any energy has been cancelled. {{-}} ==Types and operating principles== :''For a more complete list of laser types see this list of laser types.'' File:Commercial laser lines.svg
thumb
400px
Wavelengths of commercially available lasers. Laser types with distinct laser lines are shown above the wavelength bar, while below are shown lasers that can emit in a wavelength range. The color codifies the type of laser material (see the figure description for more details). ===Gas lasers=== {{Main
Gas laser}} Following the invention of the HeNe gas laser, many other gas discharges have been found to amplify light coherently. Gas lasers using many different gases have been built and used for many purposes. The helium-neon laser (HeNe) is able to operate at a number of different wavelengths, however the vast majority are engineered to lase at 633 nm; these relatively low cost but highly coherent lasers are extremely common in optical research and educational laboratories. Commercial Carbon dioxide laser
carbon dioxide (CO<sub>2</sub>) lasers can emit many hundreds of watts in a single spatial mode which can be concentrated into a tiny spot. This emission is in the thermal infrared at 10.6 µm; such lasers are regularly used in industry for cutting and welding. The efficiency of a CO<sub>2</sub> laser is unusually high: over 10%. Ion laser
Argon-ion lasers can operate at a number of lasing transitions between 351 and 528.7 nm. Depending on the optical design one or more of these transitions can be lasing simultaneously; the most commonly used lines are 458 nm, 488 nm and 514.5 nm. A nitrogen TEA laser
transverse electrical discharge in gas at atmospheric pressure (TEA) laser is an inexpensive gas laser, often home-built by hobbyists, which produces rather incoherent UV light at 337.1 nm.<ref>{{cite web
last = Csele
first = Mark
title = The TEA Nitrogen Gas Laser
work = Homebuilt Lasers Page
year=2004
url = http://www.technology.niagarac.on.ca/people/mcsele/lasers/LasersTEA.htm
accessdate =September 15, 2007
archiveurl = http://web.archive.org/web/20070911190723/http://www.technology.niagarac.on.ca/people/mcsele/lasers/LasersTEA.htm <!-- Bot retrieved archive -->
archivedate = September 11, 2007}}</ref> Metal ion lasers are gas lasers that generate deep ultraviolet wavelengths. Helium-silver (HeAg) 224 nm and neon-copper (NeCu) 248 nm are two examples. Like all low-pressure gas lasers, the gain media of these lasers have quite narrow oscillation linewidths, less than 3 GHz (0.5 picometers),<ref>{{cite web
title = Deep UV Lasers
publisher = Photon Systems, Covina, Calif
url = http://www.photonsystems.com/pdfs/duv-lasersource.pdf
accessdate =May 27, 2007
format=PDF}}</ref> making them candidates for use in fluorescence suppressed Raman spectroscopy. ====Chemical lasers==== Chemical lasers are powered by a chemical reaction permitting a large amount of energy to be released quickly. Such very high power lasers are especially of interest to the military, however continuous wave chemical lasers at very high power levels, fed by streams of gasses, have been developed and have some industrial applications. As examples, in the Hydrogen fluoride laser (2700–2900 nm) and the Deuterium fluoride laser (3800 nm) the reaction is the combination of hydrogen or deuterium gas with combustion products of ethylene in nitrogen trifluoride. ====Excimer lasers==== Excimer lasers are a special sort of gas laser powered by an electric discharge in which the lasing medium is an excimer, or more precisely an exciplex in existing designs. These are molecules which can only exist with one atom in an excited state
excited electronic state. Once the molecule transfers its excitation energy to a photon, therefore, its atoms are no longer bound to each other and the molecule disintegrates. This drastically reduces the population of the lower energy state thus greatly facilitating a population inversion. Excimers currently used are all :Category:Noble gas compounds
noble gas compounds; noble gasses are chemically inert and can only form compounds while in an excited state. Excimer lasers typically operate at ultraviolet wavelengths with major applicatons including semiconductor photolithography and LASIK eye surgery. Commonly used excimer molecules include ArF (emission at 193 nm), KrCl (222 nm), KrF (248 nm), XeCl (308 nm), and XeF (351 nm).<ref>{{cite book
first=D.
last=Schuocker
year=1998
title=Handbook of the Eurolaser Academy
publisher=Springer
isbn=0-412-81910-4 }}</ref> The molecular fluorine laser, emitting at 157 nm in the vacuum ultraviolet is sometimes referred to as an excimer laser, however this appears to be a misnomer inasmuch as F<sub>2</sub> is a stable compound. ===Solid-state lasers=== File:Green-laser-pointer-dpss-diagrams.jpg
thumb
right
A frequency-doubled green laser pointer, showing internal construction. Two AAA cells and electronics power the laser module (lower diagram) This contains a powerful 808 nm IR diode laser that optically pumps a Nd:YVO<sub>4</sub> crystal inside a laser cavity. That laser produces 1064 nm (infrared) light which is mainly confined inside the resonator. Also inside the laser cavity, however, is a non-linear KTP crystal which causes frequency doubling, resulting in green light at 532 nm. The front mirror is transparent to this visible wavelength which is then expanded and collimated using two lenses (in this particular design). Solid-state lasers use a crystalline or glass rod which is "doped" with ions that provide the required energy states. For example, the first working laser was a ruby laser, made from ruby (chromium-doped corundum). The population inversion is actually maintained in the "dopant", such as chromium or neodymium. These materials are pumped optically using a shorter wavelength than the lasing wavelength, often from a flashtube or from another laser. It should be noted that "solid-state" in this sense refers to a crystal or glass, but this usage is distinct from the designation of "solid-state electronics" in referring to semiconductors. Semiconductor lasers (laser diodes) are pumped electrically and are thus ''not'' referred to as solid-state lasers. The class of solid-state lasers would, however, properly include fiber lasers in which dopants in the glass lase under optical pumping. But in practice these are simply referred to as "fiber lasers" with "solid-state" reserved for lasers using a solid rod of such a material. Neodymium is a common "dopant" in various solid-state laser crystals, including yttrium orthovanadate (Neodymium-doped yttrium orthovanadate
Nd:YVO<sub>4</sub>), yttrium lithium fluoride (Nd:YLF) and yttrium aluminium garnet (Nd:YAG). All these lasers can produce high powers in the infrared spectrum at 1064 nm. They are used for cutting, welding and marking of metals and other materials, and also in spectroscopy and for pumping dye lasers. These lasers are also commonly nonlinear optics
frequency doubled, nonlinear optics
tripled or nonlinear optics
quadrupled, in so-called "diode pumped solid state" or DPSS lasers. Under second, third, or fourth harmonic generation these produce 532 nm (green, visible), 355 nm and 266 nm (Ultraviolet
UV) beams. This is the technology behind the bright laser pointers particularly at green (532 nm) and other short visible wavelengths. Ytterbium, holmium, thulium, and erbium are other common "dopants" in solid-state lasers. Ytterbium is used in crystals such as Yb:YAG, Yb:KGW, Yb:KYW, Yb:SYS, Yb:BOYS, Yb:CaF<sub>2</sub>, typically operating around 1020–1050 nm. They are potentially very efficient and high powered due to a small quantum defect. Extremely high powers in ultrashort pulses can be achieved with Yb:YAG. Holmium-doped YAG crystals emit at 2097 nm and form an efficient laser operating at infrared wavelengths strongly absorbed by water-bearing tissues. The Ho-YAG is usually operated in a pulsed mode, and passed through optical fiber surgical devices to resurface joints, remove rot from teeth, vaporize cancers, and pulverize kidney and gall stones. Titanium-doped sapphire (Ti-sapphire laser
Ti:sapphire) produces a highly tunable laser
tunable infrared laser, commonly used for spectroscopy. It is also notable for use as a mode-locked laser producing ultrashort pulses of extremely high peak power. Thermal limitations in solid-state lasers arise from unconverted pump power that manifests itself as heat. This heat, when coupled with a high thermo-optic coefficient (d''n''/d''T'') can give rise to thermal lensing as well as reduced quantum efficiency. These types of issues can be overcome by another novel diode-pumped solid-state laser, the diode-pumped thin disk laser. The thermal limitations in this laser type are mitigated by using a laser medium geometry in which the thickness is much smaller than the diameter of the pump beam. This allows for a more even thermal gradient in the material. Thin disk lasers have been shown to produce up to kilowatt levels of power.<ref>C. Stewen, M. Larionov, and A. Giesen, "Yb:YAG thin disk laser with 1 kW output power", in OSA Trends in Optics and Photonics, Advanced Solid-State Lasers, H. Injeyan, U. Keller, and C. Marshall, ed. (Optical Society of America, Washington, DC., 2000) pp. 35–41.</ref> ===Fiber lasers=== {{Main
Fiber laser}} Solid-state lasers or laser amplifiers where the light is guided due to the total internal reflection in a single mode optical fiber are instead called fiber lasers. Guiding of light allows extremely long gain regions providing good cooling conditions; fibers have high surface area to volume ratio which allows efficient cooling. In addition, the fiber's waveguiding properties tend to reduce thermal distortion of the beam. Erbium and ytterbium ions are common active species in such lasers. Quite often, the fiber laser is designed as a double-clad fiber. This type of fiber consists of a fiber core, an inner cladding and an outer cladding. The index of the three concentric layers is chosen so that the fiber core acts as a single-mode fiber for the laser emission while the outer cladding acts as a highly multimode core for the pump laser. This lets the pump propagate a large amount of power into and through the active inner core region, while still having a high numerical aperture (NA) to have easy launching conditions. Pump light can be used more efficiently by creating a fiber disk laser, or a stack of such lasers. Fiber lasers have a fundamental limit in that the intensity of the light in the fiber cannot be so high that optical nonlinearities induced by the local electric field strength can become dominant and prevent laser operation and/or lead to the material destruction of the fiber. This effect is called photodarkening. In bulk laser materials, the cooling is not so efficient, and it is difficult to separate the effects of photodarkening from the thermal effects, but the experiments in fibers show that the photodarkening can be attributed to the formation of long-living color centers.{{Citation needed
date=May 2008}} ===Photonic crystal lasers=== Photonic crystal lasers are lasers based on nano-structures that provide the mode confinement and the Density of states
density of optical states (DOS) structure required for the feedback to take place.{{Clarify
date=February 2009}} They are typical micrometre-sized{{dubious
date=November 2010}} and tunable on the bands of the photonic crystals.<ref>{{cite journal
title=Ultraviolet photonic crystal laser
first=X.
last=Wu
coauthors=et al.
volume=85
issue=17
date=October 25, 2004
journal=Applied Physics Letters
url=http://www.eng.yale.edu/images/ArticlPDF/APL04A.PDF
doi=10.1063/1.1808888
arxiv = physics/0406005
bibcode = 2004ApPhL..85.3657W
page=3657 }}</ref>{{Clarify
date=February 2009}} ===Semiconductor lasers=== File:Diode laser.jpg
thumb
A 5.6 mm 'closed can' commercial laser diode, probably from a CD player
CD or DVD player Semiconductor lasers are diodes which are electrically pumped. Recombination of electrons and holes created by the applied current introduces optical gain. Reflection from the ends of the crystal form an optical resonator, although the resonator can be external to the semiconductor in some designs. Commercial laser diodes emit at wavelengths from 375 nm to 3500 nm. Low to medium power laser diodes are used in laser pointers, laser printers and CD/DVD players. Laser diodes are also frequently used to optically laser pumping
pump other lasers with high efficiency. The highest power industrial laser diodes, with power up to 10 kW (70dBm){{Citation needed
date=November 2010}}, are used in industry for cutting and welding. External-cavity semiconductor lasers have a semiconductor active medium in a larger cavity. These devices can generate high power outputs with good beam quality, wavelength-tunable narrow-linewidth radiation, or ultrashort laser pulses. Vertical cavity surface-emitting lasers (VCSELs) are semiconductor lasers whose emission direction is perpendicular to the surface of the wafer. VCSEL devices typically have a more circular output beam than conventional laser diodes, and potentially could be much cheaper to manufacture. As of 2005, only 850 nm VCSELs are widely available, with 1300 nm VCSELs beginning to be commercialized,<ref>[http://lfw.pennnet.com/Articles/Article_Display.cfm?ARTICLE_ID=243400&p=12 "Picolight ships first 4-Gbit/s 1310-nm VCSEL transceivers"], ''Laser Focus World'', December 9, 2005. Retrieved May 27, 2006</ref> and 1550 nm devices an area of research. VECSELs are external-cavity VCSELs. Quantum cascade lasers are semiconductor lasers that have an active transition between energy ''sub-bands'' of an electron in a structure containing several quantum wells. The development of a silicon laser is important in the field of optical computing. Silicon is the material of choice for integrated circuits, and so electronic and silicon photonic components (such as optical interconnects) could be fabricated on the same chip. Unfortunately, silicon is a difficult lasing material to deal with, since it has certain properties which block lasing. However, recently teams have produced silicon lasers through methods such as fabricating the lasing material from silicon and other semiconductor materials, such as indium(III) phosphide or gallium(III) arsenide, materials which allow coherent light to be produced from silicon. These are called hybrid silicon laser. Another type is a Raman laser, which takes advantage of Raman scattering to produce a laser from materials such as silicon. ===Dye lasers=== Image:Coherent 899 dye laser.jpg
thumb
Close-up of a table-top dye laser based on Rhodamine 6G. Dye lasers use an organic dye as the gain medium. The wide gain spectrum of available dyes, or mixtures of dyes, allows these lasers to be highly tunable, or to produce very short-duration pulses (on the order of a few femtoseconds). Although these tunable lasers are mainly known in their liquid form, researchers have also demonstrated narrow-linewidth tunable emission in dispersive oscillator configurations incorporating solid-state dye gain media.<ref>F. J. Duarte, [http://www.opticsjournal.com/tlo.htm ''Tunable Laser Optics'' (Elsevier Academic, New York, 2003)].</ref> In their most prevalent form these solid state dye lasers use dye-doped polymers as laser media. ===Free-electron lasers=== File:FELIX.jpg
thumb
The free-electron laser ''FELIX'' at the FOM Institute for Plasma Physics Rijnhuizen, Nieuwegein Free-electron lasers, or FELs, generate coherent, high power radiation, that is widely tunable, currently ranging in wavelength from microwaves, through terahertz radiation and infrared, to the visible spectrum, to soft X-rays. They have the widest frequency range of any laser type. While FEL beams share the same optical traits as other lasers, such as coherent radiation, FEL operation is quite different. Unlike gas, liquid, or solid-state lasers, which rely on bound atomic or molecular states, FELs use a relativistic electron beam as the lasing medium, hence the term ''free-electron''. ===Bio laser=== Living cells can be genetically engineered to produce Green fluorescent protein (GFP). The GFP is used as the laser's "gain medium", where light amplification takes place. The cells are then placed between two tiny mirrors, just 20 millionths of a metre across, which acted as the "laser cavity" in which light could bounce many times through the cell. Upon bathing the cell with blue light, it could be seen to emit directed and intense green laser light.<ref>{{cite web
url=http://www.bbc.co.uk/news/science-environment-13725719
title=Laser is produced by a living cell
first=Jason
last=Palmer
date=June 13, 2011
work=BBC News
accessdate=June 13, 2011}}</ref><ref>{{cite web
url=http://www.nature.com/nphoton/journal/vaop/ncurrent/full/nphoton.2011.99.html
title=Single-cell biological lasers
author=Malte C. Gather & Seok Hyun Yun
date=June 12, 2011
work=Nature Photonics
accessdate=June 13, 2011}}</ref> ===Exotic laser media=== In September 2007, the BBC News reported that there was speculation about the possibility of using positronium annihilation to drive a very powerful gamma ray laser.<ref name="Fildes">{{cite news
url=http://news.bbc.co.uk/2/hi/science/nature/6991030.stm
title=Mirror particles form new matter
first=Jonathan
last=Fildes
date=September 12, 2007
work=BBC News
accessdate=May 22, 2008}}</ref> Dr. David Cassidy of the University of California, Riverside proposed that a single such laser could be used to ignite a nuclear fusion reaction, replacing the banks of hundreds of lasers currently employed in inertial confinement fusion experiments.<ref name="Fildes"/> Space-based X-ray lasers pumped by a nuclear explosion have also been proposed as antimissile weapons.<ref>{{cite journal
first=Jeff
last=Hecht
title=The history of the x-ray laser
journal=Optics and Photonics News
volume=19
issue=5
month=May
year=2008
publisher=Optical Society of America
pages=26–33}}</ref><ref>{{cite journal
first=Clarence A.
last=Robinson
title=Advance made on high-energy laser
journal=Aviation Week & Space Technology
issue=February 23, 1981
year=1981
pages=25–27}}</ref> Such devices would be one-shot weapons. ==Uses== File:Laser sizes.jpg
thumb
Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments. {{Main
List of applications for lasers}} When lasers were invented in 1960, they were called "a solution looking for a problem".<ref>{{cite book
title=A Century of Nature: Twenty-One Discoveries that Changed Science and the World
author= Charles H. Townes
authorlink=Charles Hard Townes
chapter=The first laser
chapterurl=http://www.press.uchicago.edu/Misc/Chicago/284158_townes.html
editor= Laura Garwin and Tim Lincoln
publisher=University of Chicago Press
year=2003
pages=107–12
isbn=0-226-28413-1
accessdate=February 2, 2008}}</ref> Since then, they have become ubiquitous, finding utility in thousands of highly varied applications in every section of modern society, including consumer electronics, information technology, science, medicine, industry, law enforcement, entertainment, and the Laser applications#Military
military. The first use of lasers in the daily lives of the general population was the supermarket barcode scanner, introduced in 1974. The laserdisc player, introduced in 1978, was the first successful consumer product to include a laser but the compact disc player was the first laser-equipped device to become common, beginning in 1982 followed shortly by laser printers. Some other uses are: * Medicine: Bloodless surgery, laser healing, surgery
surgical treatment, kidney stone treatment, Laser eye surgery (disambiguation)
eye treatment, dentistry * Industry: Cutting, welding, material heat treatment, marking parts, non-contact measurement of parts * Military: Marking targets, guiding munitions, Airborne Laser
missile defence, DIRCM
electro-optical countermeasures (EOCM), alternative to radar, blinding troops. * Law enforcement agency
Law enforcement: used for latent fingerprint detection in the forensic identification field<ref>Dalrymple B. E., Duff J. M., Menzel E. R. "Inherent fingerprint luminescence – detection by laser". ''Journal of Forensic Sciences'', 22(1), 1977, 106–115</ref><ref>Dalrymple B. E. "Visible and infrared luminescence in documents : excitation by laser". ''Journal of Forensic Sciences'', 28(3), 1983, 692–696</ref> * Research: Spectroscopy, laser ablation, laser annealing (metallurgy)
annealing, laser scattering, laser interferometry, LIDAR, laser capture microdissection, fluorescence microscopy * Product development/commercial: laser printers, optical discs (e.g. CDs and the like), barcode scanners, thermometers, laser pointers, holograms, bubblegrams. * Laser lighting displays: Laser light shows * Cosmetic surgery
Cosmetic skin treatments: acne treatment, cellulite and striae reduction, and Laser hair removal
hair removal. In 2004, excluding diode lasers, approximately 131,000 lasers were sold with a value of US$2.19 billion.<ref>Kincade, Kathy and Stephen Anderson (2005) "Laser Marketplace 2005: Consumer applications boost laser sales 10%", ''Laser Focus World'', vol. 41, no. 1. ([http://lfw.pennnet.com/Articles/Article_Display.cfm?Section=ARCHI&ARTICLE_ID=219847&VERSION_NUM=2&p=12 online])</ref> In the same year, approximately 733 million diode lasers, valued at $3.20 billion, were sold.<ref>Steele, Robert V. (2005) "Diode-laser market grows at a slower rate", ''Laser Focus World'', vol. 41, no. 2. ([http://lfw.pennnet.com/Articles/Article_Display.cfm?Section=ARCHI&ARTICLE_ID=221439&VERSION_NUM=4&p=12 online])</ref> ===Examples by power=== File:Lying down on the VLT platform.jpg
thumb
upright
Laser application in astronomical adaptive optics imaging Different applications need lasers with different output powers. Lasers that produce a continuous beam or a series of short pulses can be compared on the basis of their average power. Lasers that produce pulses can also be characterized based on the ''peak'' power of each pulse. The peak power of a pulsed laser is many orders of magnitude greater than its average power. The average output power is always less than the power consumed. {
class="wikitable"
+ The continuous or average power required for some uses:
- ! Power !! Use
-
align=right
{{nowrap
1–5 mW}}
Laser pointers
-
align=right
{{nowrap
5 mW}}
CD-ROM drive
-
align=right
{{nowrap
5–10 mW}}
DVD player or DVD-ROM drive
-
align=right
{{nowrap
100 mW}}
High-speed CD-RW burner
-
align=right
{{nowrap
250 mW}}
Consumer 16× DVD-R burner
-
style="text-align:right;" rowspan="2"
{{nowrap
400 mW}}
Burning through a jewel case including disk within {{nowrap
4 seconds}}<ref>{{cite web
url=http://www.youtube.com/watch?v=zhtpYztY8-c
title=Green Laser 400 mW burn a box CD in 4 second
work=youtube
accessdate=December 10, 2011}}</ref>
-
DVD 24× dual-layer recording.<ref>{{cite web
url=http://elabz.com/laser-diode-power-output-based-on-dvd-rrw-specs/
title=Laser Diode Power Output Based on DVD-R/RW specs
publisher=elabz.com
accessdate=December 10, 2011}}</ref>
-
align=right
{{nowrap
1 W}}
Green laser in current Holographic Versatile Disc prototype development
-
align=right
{{nowrap
1–20 W}}
Output of the majority of commercially available solid-state lasers used for Micromachinery
micro machining
-
align=right
{{nowrap
30–100 W}}
Typical sealed CO<sub>2</sub> surgical lasers<ref>George M. Peavy, "[http://www.veterinary-laser.com/expert-opinion.php How to select a surgical veterinary laser]", veterinary-laser.com. URL accessed March 14, 2008.</ref>
-
align=right
{{nowrap
100–3000 W}}
Typical sealed CO<sub>2</sub> lasers used in industrial laser cutting
-
align=right
{{nowrap
100 kW}}
Claimed output of a CO<sub>2</sub> laser being developed by Northrop Grumman for military (weapon) applications
} Examples of pulsed systems with high peak power: * 700 terawatt
TW (700×10<sup>12</sup> W) – National Ignition Facility, a 192-beam, 1.8-megajoule laser system adjoining a 10-meter-diameter target chamber.<ref>Heller, Arnie, "[http://www.llnl.gov/str/JulAug05/VanArsdall.html Orchestrating the world's most powerful laser]." ''Science and Technology Review''. Lawrence Livermore National Laboratory, July/August 2005. URL accessed May 27, 2006.</ref> * 1.3 petawatt
PW (1.3×10<sup>15</sup> W) – world's most powerful laser as of 1998, located at the Lawrence Livermore Laboratory<ref>{{cite web
url=http://newton.ex.ac.uk/aip/physnews.401.html#3
title=Physics News Update 401
accessdate=March 15, 2008
last=Schewe
first=Phillip F.
coauthors=Stein, Ben
date=November 9, 1998
publisher=American Institute of Physics }}</ref> ===Hobby uses=== In recent years, some hobbyists have taken interests in lasers. Lasers used by hobbyists are generally of class IIIa or IIIb (see #Safety
Safety), although some have made their own class IV types.<ref>[http://www.powerlabs.org/laser.htm PowerLabs CO<sub>2</sub> LASER!] Sam Barros June 21, 2006. Retrieved January 1, 2007.</ref> However, compared to other hobbyists, laser hobbyists are far less common, due to the cost and potential dangers involved. Due to the cost of lasers, some hobbyists use inexpensive means to obtain lasers, such as salvaging laser diodes from broken DVD players (red), Blu-ray players (violet), or even higher power laser diodes from CD or DVD burners.<ref>{{cite web
url=http://www.felesmagus.com/pages/lasers-howto.html
title=Howto: Make a DVD Burner into a High-Powered Laser
publisher=Felesmagus.com
accessdate=December 10, 2011}}</ref> Hobbyists also have been taking surplus pulsed lasers from retired military applications and modifying them for pulsed holography. Pulsed Ruby and pulsed YAG lasers have been used. ==Safety== File:DIN 4844-2 Warnung vor Laserstrahl D-W010.svg
thumb
200px
Warning symbol for lasers File:Laser label 2.jpg
thumb
200px
Laser warning label {{Main
Laser safety}} Even the first laser was recognized as being potentially dangerous. Theodore Maiman characterized the first laser as having a power of one "Gillette" as it could burn through one Global Gillette
Gillette razor
razor blade. Today, it is accepted that even low-power lasers with only a few milliwatts of output power can be hazardous to human eyesight, when the beam from such a laser hits the eye directly or after reflection from a shiny surface. At wavelengths which the cornea and the lens can focus well, the coherence and low divergence of laser light means that it can be focused by the human eye
eye into an extremely small spot on the retina, resulting in localized burning and permanent damage in seconds or even less time. Lasers are usually labeled with a safety class number, which identifies how dangerous the laser is: *Class 1 is inherently safe, usually because the light is contained in an enclosure, for example in CD players. *Class 2 is safe during normal use; the blink reflex of the eye will prevent damage. Usually up to 1 mW power, for example laser pointers. *Class 3R (formerly IIIa) lasers are usually up to 5 mW and involve a small risk of eye damage within the time of the blink reflex. Staring into such a beam for several seconds is likely to cause damage to a spot on the retina. *Class 3B can cause immediate eye damage upon exposure. *Class 4 lasers can burn skin, and in some cases, even scattered light can cause eye and/or skin damage. Many industrial and scientific lasers are in this class. The indicated powers are for visible-light, continuous-wave lasers. For pulsed lasers and invisible wavelengths, other power limits apply. People working with class 3B and class 4 lasers can protect their eyes with safety goggles which are designed to absorb light of a particular wavelength. Infrared lasers with wavelengths beyond about 1.4 micrometres are often referred to as "eye-safe", because the cornea strongly absorbs light at these wavelengths, protecting the retina from damage. The label "eye-safe" can be misleading, however, as it only applies to relatively low power continuous wave beams; a high power or Q-switched laser at these wavelengths can burn the cornea, causing severe eye damage, and even moderate power lasers can injure the eye. ==As weapons== Image:THEL-ACTD.jpg
thumb
300px
The US-Israeli Tactical High Energy weapon has been used to shoot down rockets and artillery shells. Lasers of all but the lowest powers can potentially be used as incapacitating weapons, through their ability to produce temporary or permanent vision loss in varying degrees when aimed at the eyes. The degree, character, and duration of vision impairment caused by eye exposure to laser light varies with the power of the laser, the wavelength(s), the collimation of the beam, the exact orientation of the beam, and the duration of exposure. Lasers of even a fraction of a watt in power can produce immediate, permanent vision loss under certain conditions, making such lasers potential non-lethal but incapacitating weapons. The extreme handicap that laser-induced blindness represents makes the use of lasers even as non-lethal weapons morally controversial, and weapons designed to cause blindness have been banned by the Protocol on Blinding Laser Weapons. Incidents of pilots being exposed to lasers while flying have prompted aviation authorities to implement special procedures to deal with such hazards.<ref>{{cite news
url=http://news.bbc.co.uk/1/hi/technology/7990013.stm
work=BBC News
title=Police fight back on laser threat
date=April 8, 2009
accessdate=April 4, 2010}}</ref> Laser weapons capable of directly damaging or destroying a target in combat are still in the experimental stage. The general idea of laser-beam weaponry is to hit a target with a train of brief pulses of light. The rapid evaporation and expansion of the surface causes shockwaves that damage the target.{{Citation needed
date=November 2010}} The power needed to project a high-powered laser beam of this kind is beyond the limit of current mobile power technology, thus favoring chemically powered gas dynamic lasers. Example experimental systems include MIRACL and the Tactical High Energy Laser. The U.S. Air Force was working on the Boeing YAL-1, an airborne laser mounted in a Boeing 747. It was intended to be used to shoot down incoming ballistic missiles over enemy territory. On March 18, 2009 Northrop Grumman claimed that its engineers in Redondo Beach, California
Redondo Beach had successfully built and tested an electrically powered solid state laser capable of producing a 100-kilowatt beam, powerful enough to destroy an airplane. According to Brian Strickland, manager for the United States Army's Joint High Power Solid State Laser program, an electrically powered laser is capable of being mounted in an aircraft, ship, or other vehicle because it requires much less space for its supporting equipment than a chemical laser.<ref>{{cite web
first=Pae
last= Peter
title=Northrop Advance Brings Era Of The Laser Gun Closer
work=Los Angeles Times
date=March 19, 2009.
page= B2
url=http://articles.latimes.com/2009/mar/19/business/fi-laser19 }}</ref> However the source of such a large electrical power in a mobile application remains unclear. The YAL-1 program was canceled due to infeasibility in December 2011. The United States navy is developing a laser weapon referred to as the Laser Weapon System or LaWS.<ref>{{cite news
title=Navy's New Laser Weapon Blasts Bad Guys From Air, Sea
author=Luis Martinez
url=http://news.yahoo.com/navys-laser-weapon-blasts-bad-215808231.html
newspaper=American Broadcasting Company
ABC
date=09 APR 2013
accessdate=9 April 2013}}</ref> ==Fictional predictions== {{See also
Raygun}} Image:Raygun.svg
thumb
right
A typical imaginary raygun Several novelists described devices similar to lasers, prior to the discovery of stimulated emission: *A very early example is the Heat-Ray featured in H. G. Wells' novel ''The War of the Worlds (novel)
The War of the Worlds'' (1898).<ref name="Van Riper 46">Van Riper, op.cit., p. 46.</ref> *A laser-like device was described in Alexey Tolstoy's science fiction novel ''The Hyperboloid of Engineer Garin'' in 1927. *Mikhail Bulgakov exaggerated the biological effect (laser bio stimulation) of intense red light in his science fiction novel ''Fatal Eggs'' (1925), without any reasonable description of the source of this red light. (In that novel, the red light first appears occasionally from the illuminating system of an advanced microscope; then the protagonist Prof. Persikov arranges a special set-up for generation of the red light.) ==See also== {{multicol}} * Bessel beam * Coherent perfect absorber * Dazzler (weapon) * Free-space optical communication * Homogeneous broadening * Induced gamma emission * Injection seeder * International Laser Display Association * Laser accelerometer * Lasers and aviation safety {{multicol-break}} * Laser beam profiler * Laser bonding * Laser converting * Laser cooling * Laser engraving * Laser medicine * Laser scalpel * 3D scanner * Laser turntable * Laser beam welding * List of laser articles * List of light sources {{multicol-break}} * Maser * Mercury laser * Nanolaser * Reference beam * Rytov number * Sound Amplification by Stimulated Emission of Radiation * Selective laser sintering * Spaser * Speckle pattern * Tophat beam {{multicol-end}} ==References== {{reflist
30em}} ==Further reading== :'''Books''' *Bertolotti, Mario (1999, trans. 2004). ''The History of the Laser'', Institute of Physics. ISBN 0-7503-0911-3 *Bromberg, Joan Lisa (1991). ''The Laser in America, 1950–1970'', MIT Press. ISBN 978-0-262-02318-4 *Csele, Mark (2004). ''Fundamentals of Light Sources and Lasers'', Wiley. ISBN 0-471-47660-9 *Koechner, Walter (1992). ''Solid-State Laser Engineering'', 3rd ed., Springer-Verlag. ISBN 0-387-53756-2 *Siegman, Anthony E. (1986). ''Lasers'', University Science Books. ISBN 0-935702-11-3 *William T. Silfvast
Silfvast, William T. (1996). ''Laser Fundamentals'', Cambridge University Press. ISBN 0-521-55617-1 *Svelto, Orazio (1998). ''Principles of Lasers'', 4th ed. (trans. David Hanna), Springer. ISBN 0-306-45748-2 *{{cite book
last=Taylor
first=Nick
title=LASER: The inventor, the Nobel laureate, and the thirty-year patent war
year=2000
publisher=Simon & Schuster
location=New York
isbn=0-684-83515-0 }} *Wilson, J. & Hawkes, J.F.B. (1987). ''Lasers: Principles and Applications'', Prentice Hall International Series in Optoelectronics, Prentice Hall. ISBN 0-13-523697-5 *Yariv, Amnon (1989). ''Quantum Electronics'', 3rd ed., Wiley. ISBN 0-471-60997-8 :'''Periodicals''' *''Applied Physics B: Lasers and Optics'' ({{ISSN
0946-2171}}) *''IEEE Journal of Lightwave Technology'' ({{ISSN
0733-8724}}) *''IEEE Journal of Quantum Electronics'' ({{ISSN
0018-9197}}) *''IEEE Journal of Selected Topics in Quantum Electronics'' ({{ISSN
1077-260X}}) *''IEEE Photonics Technology Letters'' ({{ISSN
1041-1135}}) *''Journal of the Optical Society of America B: Optical Physics'' ({{ISSN
0740-3224}}) *''Laser Focus World'' ({{ISSN
0740-2511}}) *''Optics Letters'' ({{ISSN
0146-9592}}) *''Photonics Spectra'' ({{ISSN
0731-1230}}) ==External links== {{Commons category
Lasers}} *[http://www.rp-photonics.com/encyclopedia.html Encyclopedia of laser physics and technology] by Dr. Rüdiger Paschotta *[http://www.repairfaq.org/sam/lasersam.htm A Practical Guide to Lasers for Experimenters and Hobbyists] by Samuel M. Goldwasser *[http://www.technology.niagarac.on.ca/staff/mcsele/lasers/index.html Homebuilt Lasers Page] by Professor Mark Csele *[http://space.newscientist.com/article/dn13634-powerful-laser-is-brightest-light-in-the-universe.html?feedId=online-news_rss20 Powerful laser is 'brightest light in the universe'] – The world's most powerful laser as of 2008 might create supernova-like shock waves and possibly even antimatter (''New Scientist'', April 9, 2008) *[http://www.instructables.com/id/Laser-Flashlight-Hack!!/ Homemade laser project] by Kip Kedersha *"[http://prn1.univ-lemans.fr/prn1/siteheberge/optique/M1G1_FBalembois_ang/co/M1G1_anglais_web.html The Laser: basic principles]" an online course by Prof. F. Balembois and Dr. S. Forget. ''Instrumentation for Optics'', 2008 *[http://www.irconnect.com/noc/press/pages/news_releases.html?d=154600 Northrop Grumman's Press Release on the Firestrike 15kw tactical laser product.] *[http://www.laserfest.org Website on Lasers 50th anniversary by APS, OSA, SPIE] *[http://www.advancingthelaser.org Advancing the Laser anniversary site by SPIE: Video interviews, open-access articles, posters, DVDs] *[http://www.aip.org/history/exhibits/laser/sections/raydevices.html Bright Idea: The First Lasers] *[https://nanohub.org/resources/laserdyn Free software for Simulation of random laser dynamics] *[http://ocw.mit.edu/resources/res-6-006-video-demonstrations-in-lasers-and-optics-spring-2008/ Video Demonstrations in Lasers and Optics] Produced by the Massachusetts Institute of Technology (MIT). Real-time effects are demonstrated in a way that would be difficult to see in a classroom setting. *[http://spie.org/x39914.xml Virtual Museum of Laser History, from the touring exhibit by SPIE] *[http://www.toutestquantique.fr/#laser website with animations, applications and research about laser and other quantum based phenomena] Universite Paris Sud Category:Lasers
Category:American inventions Category:Directed-energy weapons Category:Forensic equipment Category:Photonics Category:Quantum optics Category:Acronyms {{Link GA
ru}} {{Link FA
af}} {{Link FA
bar}}