

<==== Sam's Laser FAQ ====>



Safety, Info, Links, Parts, Types, Drive, Construction A Practical Guide to Lasers for Experimenters and Hobbyists

Back to Sam's Laser FAQ Table of Contents. Foreword Sam's Laser FAQ evolved to become what it is today from a short note on safely powering low power laser diodes which I had written around 1996 in conjunction with the CD player repair guide (part of the Sci.Electronics.Repair FAQ). Those laser diodes were usually ripped from dead CD players - this was before pocket laser pointers could be found in cereal boxes. :) (If you're really curious, that short note and a couple of other early versions of Sam's Laser FAQ can be found at Sam's Laser FAQ Archive, typos and all.) Chapters were added as I acquired a variety of lasers and related equipment. Thus, much of this information comes from first-hand experience. First those little laser diodes and driver circuits, then helium-neon lasers and power supplies, followed by argon ion lasers, Nd:YAG lasers, DPSS lasers, and who knows what else the future will bring. However, many others have contributed in one form or another (newsgroup postings, email, laser parts, etc.). They are cited in the Acknowledgments and/or in the individual sections which contain their material. And, by the way, the name: "Sam's Laser FAQ" was more or less created by those who have read and commented on it via the newsgroups or direct email. The name stuck in part because the original one: LASERS: Safety, Info, Links, Parts, Types, Drive, Construction" was just way too long. :) While I had kept in touch with laser technology since their invention in the early 1960s, my direct contact with lasers was relatively limited until much more recently. Although there was the glass working I did for someone else's home-built HeNe laser, the ruby laser I inherited at my high school because no one else wanted it, and the little commercial HeNe laser there used to view the hologram in an issue of Scientific American, I was not yet really hooked on lasers. In fact, the first real lasers that I actually owned were purchased from a surplus outfit in 1990 or so - a couple of small helium-neon laser tubes and power supplies. I only bought those because a friend of mine had casually mentioned that I didn't have any lasers. I couldn't let that statement stand without doing something! Well, after mounting, wiring (which wasn't much), and testing them, I thought to myself: Well, these are kind of cool and might even come in handy someday. (My friend quickly lost interest once he realized they weren't powerful enough to burn anything!) I dragged them out every so often to make sure they still worked but that was about it, laser-wise, for awhile. Then a few years later, having spent a lot of time on the USENET newsgroups answering questions (mostly those in the sci.electronics hierarchy, sci.optics, alt.lasers, and the like), it became clear that there was virtually NO practical laser related information on the Web. Even with my somewhat limited contact with lasers, the scary thing was that it would appear that I already had more of this sort of hands-on knowledge than was available in cyberspace - and probably anywhere else outside the laser industry. Sure, the major laser manufacturers were beginning to discover the Internet for their sales and advertising, and there were some academic and research sites as well. But, if what you wanted was to be able to light up a HeNe laser tube or build a power supply for one, wire up a laser diode without blowing it out, do anything with an argon ion laser or diode pumped solid state laser, or (gasp!) build a laser from scratch - forget it. There was virtually nothing to be found on-line and only a bit more in print. Much of what did exist (on the Web at least) was incorrect, incomplete, dangerous, or all of the above. (There is more history below.) Sam's Laser FAQ is NOT an academic paper or reference work on quantum mechanics, gas discharges, or solid state physics. You can relax. It is about getting your hands into lasers safely and on a realistic budget. There is only a bare minimum of heavy math and only a few equations. The dozens of thick, expensive technical books and thousands of research papers on basic laser science and advanced laser technology exist to handle that! Sam's Laser FAQ is for the experimenter, hobbyist, weekend tinkerer, and budding mad scientist. For you! Enjoy. :)



Special thanks to MrGizmos for providing the opportunity for me to evaluate new and interesting lasers and related equipment including those from Coherent, Lightwave Electronics, Spectra-Physics, and others.

Special thanks to Cascade Laser Corp. for the contribution of an HP and Zygo HeNe laser.

Extra special thanks to Phil Bergeron at the University of South Florida for both stimulating discussions and helping and encouraging me to obtain, test, and document numerous interesting lasers over the last few years.

And finally, much appreciated thanks to Aerotech, Inc., who no doubt didn't realize it at the time and almost certainly still has no idea. But but various HeNe lasers and power supplies from their dumpster(s) in the mid-1990s (probably when they discontinued their HeNe laser operations) provided much of the initial material for the Laser FAQ, especially in the chapter on HeNe lasers! :-) In fact, the Laser FAQ would probably not exist had several cartons of HeNe laser items not been dumped on my doorstep around 1997.



Back to Preface Sub-TOC. More on My Background and What I Do for a Real Job I am an electrical engineer by profession. I have spent significant time in both academia and industry teaching and designing in the areas of the architecture and implementation of digital systems. The development of one particular special purpose high performance image and graphics processor with three of my students led to the creation of a business plan. I have done the startup thing, been taken over by a big company, spent some time there, and become bored with corporate life. As with many large companies, upper management was behaving in classic Dilbert style, with chronic and terminal foot-in-rear-end disease. They were thus incapable of appreciating the need for the next generation system that would have been zillions of times better in every respect than what was being sold and could have maintained the company's leadership position in high performance three-dimensional visualization. While my official title had a "Technical Director" in it, I had little to direct, technically or otherwise! So, out of boredom, I turned to the then still somewhat novel means of communication, the Internet. (Yes, I know, the Internet goes back to the 1970s but Mosaic, the predecessor of Netscape, was kind of new in 1994.) I discovered USENET newsgroups, in particular, the sci.electronics hierarchy including sci.electronics.repair; alt.home.repair and misc.consumers.house; and alt.lasers. I initially gravitated to the repair newsgroups because I had always been interested in repair of almost anything mechanical and electronic. During the next few years, I replied to literally 10s of thousands of questions on electronics and electronics repair, as well as some on lasers - check them out by searching on Google Groups. At some point, Filip "I'll buy a vowel" Gieszczykiewicz (filipg@repairfaq.org) contacted me via email and asked if I'd like to upload some of my material to his Web site which hosted the original Sci.Electronics FAQ. Thus were born what are now the Sci.Electronics.Repair FAQs including the "Notes on the Troubleshooting and Repair of..." series and other documents on electronics. (Fil still hosts our main S.E.R FAQ site at repairfaq.org.) As noted in the Foreword, while replying to a few questions on lasers, it became obvious that there wasn't much reliable information on practical aspects of lasers on the Internet (the Web and newsgroups). CD players and CDROM drives contained laser diodes so the first laser document to be written was one on the care and feeding of laser diodes removed from CD players. When questions were posted on Helium-Neon (HeNe) lasers, I dug up my surplus lasers and answered as best as I could - which was still usually better than what others could provide (though given what I know now, probably not much better!). Sam's Laser FAQ really took off when I was given a bunch of HeNe laser heads and power supplies - several of which I could reverse engineer. And the rest, as they say, is history! :) I officially quit the corporate World in 1996 and during the next few years devoted the bulk of my time to developing the S.E.R FAQ in general, but mostly - and increasingly - specifically Sam's Laser FAQ. I was also an independent engineering consultant, accepting the occasional contract job if I thought it would be technically fun and rewarding and paid at least enough to make any hassles tolerable. Near the end of 2000, I began working at Drexel University (Philadelphia, PA) as a Research Professor in the Center for Microwave and Lightwave Engineering (CMLE), in the Electrical and Computer Engineering (ECE) Department. I had done my undergraduate work at Drexel during a time long long ago and contacted their alumni relations department in search of some server space to mirror the S.E.R FAQ. During a meeting to discuss the matter, I casually asked if anyone was doing anything with lasers. They introduced me to of all people, the professor who amazingly had been my academic adviser from back then and he even remembered me! As it turned out, there was a need for someone with practical laser experience. I hadn't intended to get a real job but after taking some time to think it through, the idea of being back in academia had a certain appeal and I decided to give it a shot. So, now I do real laser work in a university setting. Should you care, the research involves high performance mode-locked and chirped solid state microchip lasers for millimeter wave communications, lidar/radar, and biomedical imaging. There are some papers at the CMLE Web site (which I just happen to maintain as well) with much more information. Since this is not a tenure track faculty position, I don't have to teach classes, attend faculty meetings, deal with academic politics, or have quite the pressure to publish or perish. I've been down that road and am not eager to repeat it. However, I have a couple of very talented graduate students and although I don't really own them, we make a great team with their theoretical knowledge complementing my practical experience. And, they are really impressed when I produce any sort of visible laser (especially green ones) from my pocket (everything we do at CMLE so far is in the infra-red). The only down-side was that since Research Professor is actually a staff (not a faculty) position, my status ranked somewhere between that of a garden slug and slime dwelling worm in the university hierarchy. :) In fact, as of the Summer of 2005, I am simply a consultant to Drexel and the CMLE group, no longer being officially on the staff. In addition to the Drexel work, I continue to do the occasional engineering consulting (same criteria for acceptance of jobs apply - there has to be a fun factor involved!). But enhancement of Sam's Laser FAQ still represents a major portion of my efforts. I expect this to continue for the foreseeable future.



Back to Preface Sub-TOC. Sam's Laser Lab and Lasers It would be nice if I had a lab setup like the one I outline in the chapter: Amateur Laser Construction. However, so far, that isn't the case. My laser projects have shared space with old VCRs and parts storage, the laundry area, woodworking tools, and just random junk. I have cleared out the photo equipment from my (former) darkroom to make way for lasers. (Who does wet photography anymore? I even recycled parts of my home-built enlarging timer: its relays went into a home-built argon ion laser power supply and its aluminum box is now the chassis for a lab style HeNe laser power supply.) But even with this extra space, the general appearance is more like the aftermath of a hurricane than something one might call orderly. However, the dead VCRs have fnally been evicted. :) I currently own a variety of lasers including numerous HeNe laser tubes, heads, and complete lasers (including other colors than red) from very small to fairly large, and commercial and home-built power supplies; and several air-cooled argon ion laser heads, my home-built power supply, and a still-in-need-of-reassembly Omni-150. I have countless laser diodes and a few complete modules, pulsed Nd:YAG heads with a home-built power supply, a high power CW Nd:YAG head in need of a new arc lamp (and a small miracle which will probably never happen), several DPSS green lasers (both commercial and home-built), and external mirror HeNe lasers using tubes with one and two Brewster windows mounted in home-built resonators (including a nifty one-Brewster tube that does green!). My oldest commercial laser is a Spectra-Physics model 130B HeNe laser built like a tank which has a manual dated 1966 (though I don't know if my actual sample is quite that old. Best of all, after a bit of tender loving care, it actually still lases. I do not know of any other working 130B lasers with an original tube in the explored Universe. The next oldest is an American Optical 3100 HeNe laser - also the only known working sample of this laser still in existence. I power up both these lasers daily at least for a few seconds to show I still care about them. This appears to be the attention they desire and performance continues to be unchanged, even after several years for the 130B. (As of 2010, the SP-130B still lases, barely. The AO-3100 lights up but does not lase, possibly due to degradation of the soft-coated mirrors, which are unprotected. The discharge color looks normal.) However, I've since acquired several samples of the Spectra-Physics 119 stabilized HeNe laser, which are of similar vintage. Two of these still work fine, with output power easily exceeding the original specifications. Most of the more interesting lasers are described in one form or another somewhere in this document. Wavelengths for the lasers I have or have tested so far include: 325 nm, 337.1 nm, 400 nm, 405 nm, 445 nm, 457 nm, 458 mm, 473 nm, 488 nm, 514.5 nm, 532 nm, 543.5 nm, 568 nm, 594.1 nm, 604.6 nm, 611.9 nm, 629.4 nm, 632.8 nm, 635 nm, 640 nm, 647 nm, 658 nm, 670 nm, 694.3 nm, 780 nm, 808 nm, 830 nm, 870 nm, 980 nm, 1,064 nm, 1,321 nm, 1,523.1 nm, 3,391 nm, and 10,600 nm. If you don't recognize all (or any!) of these wavelengths now, you will by the time you have read through Sam's Laser FAQ! There are many others I've seen, but they aren't as well known as these, are lower power lines in common lasers, or may be from lasers designed for custom applications. And, if you are at all curious, my favorite wavelength is 594.1 nm, which is something along the lines of traffic-light yellow. :-) Many of these lasers and laser related equipment have been given to me by various generous people as a sort of reimbursement for the vast amount of free information I have provided on-line - both in Sam's Laser FAQ and the other documents on consumer electronics repair and general electronics information (all part of the Sci.Electronics.Repair FAQ) and from my numerous contributions to the various USENET newsgroups including alt.lasers, sci.optics, sci.electronics.repair, and other technical forums (over 30,000 postings to date, most being replies to requests for assistance in various areas). I also buy occasional junk lasers on eBay or mail order but some of the most interesting ones have been sent to me in response to my request for such toys. :) (See the section: Please Don't Scrap Your Unwanted or Broken Lasers or Laser Related Equipment and Parts!.) At some point in the future I do plan to construct some truly home-built lasers, probably starting with the more unusual ones outlined in the chapter: Home-Built Pulsed Multiple Gas (PMG) Laser. I have a several vacuum pumps and gauges, and neon sign transformers, and a wide variety of suitable electronic components, but still need to put together a proper gas delivery system and acquire the required special gases. If only politicians generated more than hot air. :) Oh, and to find the time!



Back to Preface Sub-TOC. Please Don't Scrap Your Unwanted or Broken Lasers or Laser Related Equipment and Parts! For awhile this section was titled: "Searching for Good Home for Some of My Lasers or Laser Related Equipment and Parts!" but much of that stuff has found a place somewhere. Eventually it happens to us all. I was attempting to downsize - destuff the house and a variety of lasers and laser related items had to go. Some were sold (mostly on eBay) while others in more of the junk category were given away. I've already scrapped a lot of (mostly non-laser) stuff that I have not touched in many years and this pains me no end. But the place is a lot less cluttered. :) And there are still laser items that I am still interested in acquiring including various stabilized HeNe lasers, expecially types and models that are not already documented in the Laser FAQ, and samples of Ring Laser Gyros (RLGs) including those from Honeywell, Sperry, and others - or from research prrojects though these tend to be a bit large for my space. Actual RLG devices are very poorly documented in publically available literature and extremely rare surplus. I'm working to remedy the former at least and there is much more info than there used to be in the chapter: Laser Instruments and Applications starting with "Ring Laser Gyros" and in the Laser Equipment Gallery under "Helium-Neon Ring Laser Gyros". :) So, please contact me (Sam) via the Sci.Electronics.Repair FAQ Email Links Page if you have any interest in helping out either way. ;-)



Back to Preface Sub-TOC. Request for Computer Resources in Support of Sam's Laser FAQ Development I'm keeping the following as a place holder and FYI. At the present time I do not have a need for additional resources. :) Most of the text/html content for the Sci.Electronics.Repair FAQ and Sam's Laser FAQ is developed in emacs on a unix system via telnet/ssh. While some people may consider such an arrangement archaic, this allows for rapid creation and editing, accessibility to the original files from anywhere in the Universe via an Internet connection, less need to upload or download files to my PC, and professionally managed system maintenance, upgrades, and backup. I currently have access to accounts at the University of Pennsylvania (UPenn) and Drexel University which I use to create, edit, and test the material in the Sci.Electronics.Repair FAQ and Sam's Laser FAQ. The primary account I use for FAQ development is at UPenn and this seems to be secure for the moment the situation can change from one year to the next. The Drexel computer is probably reliable as far as a long term relationship but for some reason, USENET access is limited and posting doesn't seem to work at all. Therefore, I am looking for access to 1 or 2 additional unix or linux systems, preferably at academic institutions like colleges or universities, but I will also consider other types of not-for-profit organizations. For obvious reasons, I really do not want to do this in association with anything commercial. My needs are modest: 1 GB of disk space, telnet or ssh, ftp or sftp, emacs/gnus read/post, muttmail, and publicly accessible Web space. Most of what I do is editing and email so processing requirements are modest and shouldn't impact other activities. However, a reliable supported environment is critical to my sanity so your personal server farm isn't something of much interest. :) I do not want and will not accept monetary contributions for this effort. But, a way to help the FAQ development would be to provide stable computer access. If you know of, or are able to offer such a resource, please contact me via the Sci.Electronics.Repair FAQ Email Links Page. In return, of course, you get a local copy of the absolutely latest and greatest versions of the FAQs (and space permitting), all the associated ancillary material. And, of course, priority email replies to technical questions! Thank you! :)



Back to Sam's Laser FAQ Table of Contents.

Back to Preface Sub-TOC.

Back to Introduction Sub-TOC. Scope and Purpose of This Document Many types of lasers are used in conjunction with popular hobbyist projects, basement experimentation, and just plain old late night tinkering. Diode and helium-neon (HeNe) lasers in particular are very common due to several factors including the wide availability of inexpensive components and systems (new and surplus) and the relative ease of constructing working devices. A greater number of argon (and krypton) ion lasers are turning up on the surplus market at very affordable prices as they are replaced with more modern solid state alternatives like green diode pumped solid state lasers. But even some of those are now becoming available at prices that while not exactly low, are well within the reach of a dedicated hobbyist. There is often interest in carbon dioxide lasers because of their higher power capability. And, of course, ruby and YAG lasers for their higher pulsed power. However, on-line and print resources with detailed information on driving laser diodes and powering helium-neon lasers seem to be scarce. Some of those that do exist are incorrect and potentially dangerous (or at least destructive). There appears to be virtually nothing at all on argon/krypton ion, CO2, solid state, and other lasers. And, even less on the nitty-gritty of amateur laser construction. This document was written in the hopes of rectifying this situation. Contributions in almost any form are always welcome and will be acknowledged appropriately. However, note that there is, and never will be, more than passing mention of laser weapons in Sam's Laser FAQ. This is NOT the place to go to learn about such things. If that's your main interest, you'll have to look elsewhere, sorry.



Back to Introduction Sub-TOC. Organization of This Document For the most part, we assume that you are at least familiar with the basic concept of what a laser is and have an idea of your intended application (but reading though this document may help) - be it for optics experimentation, communications, ranging, simple curiosity, or just being able to say you have a working laser in the house. :-) PART I includes some general information on lasers and laser related topics. In addition to essential laser safety information, there are general items of interest, discussions of a variety of laser instruments and applications, and a list of suggested laser and laser based experiments and projects. There isn't much in the way of laser physics and other theoretical topics. (You can now breathe a sigh of relief!) Nor will there be extensive treatment of the design of laser shows, holography experiments, interferometers, or the like - though some ideas are provided just to stimulate your interest. I leave these to the many excellent books and articles that have been published over the years. Our major emphasis is on the practical aspects of common lasers (including diode, HeNe, argon/krypton ion, CO2, HeCd, and diode and lamp pumped solid state) that may be found outside of a well funded research lab - those available at reasonable cost on the used or surplus market, for example. PART II provides access to the rest of the World in terms of laser information, and laser and parts manufacturers, sales, and service. (I would include the rest of the Universe but my interstellar network is still in beta testing.) There are extensive lists of references and Web links to laser safety sites, tutorials on lasers and laser related topics, and laser and optics organizations and manufacturers. If you are interested in detailed information on all types of lasers, laser applications, laser physics, laser experiments, or laser research, consult the chapter: Laser Information Resources for a list of books, magazine articles, and Web links covering everything laser related from basic questions like "What is a laser" or "How do lasers work" to "Spectra in stimulated emission of rare gases" and "Dissociative excitation transfer and laser oscillation in RF discharges" - and everything in between. A quick check of some of the educational Web sites may provide everything you need. The chapter Laser and Parts Sources includes pointers to sources for everything from $2 laser diodes to $100,000 CO2 laser based machining centers - new, used, surplus, and salvage. PART III deals with the care and feeding of lasers constructed from commercial components like helium-neon tubes and laser diodes. There is also extensive information on the design and construction of power supply, driver, and other circuits. The chapters on specific types of lasers includes at least *10* circuits for driving laser diodes, *20* complete schematics for helium-neon laser power supplies, as well as simple modulators and other useful goodies. Most of these have been tested and/or came from working commercial designs and can be built using readily available inexpensive parts. The material on argon/krypton ion lasers includes extensive information on the general characteristics and features, power supply requirements and design considerations including circuit descriptions, and maintenance and alignment of these highly prized devices. There are several complete ion laser power schematics of varying levels of sophistication which can be replicated using readily available parts or used as the basis for a custom design of your own! There is also coverage of CO2 lasers (including a discussion of sealed CO2 tubes which are powered in a very similar way to helium-neon lasers) as well as some basic info on HeCd lasers. Solid state lasers are now dealt with in considerable detail along with complete schematics for ruby and Nd:YAG power supplies. To the best of my knowledge, no other resource in the explored universe (or elsewhere) currently comes close to providing as much practical information on these topics in a form which is both easy to read and readily accessible in one place - if at all. PART IV is for the true basement experimenter and provides information on actually constructing entire lasers from basic materials like beach sand and copper ore. :-) Well, maybe not quite that basic but: glass tubing, mirrors, hardware, gases, chemicals, and electronic components like transformers, resistors, capacitors, and diodes - and laser safety and high voltage warning signs! Where you really think constructing a laser from scratch would be a challenge, fun, and educational, first keep in mind that such an endeavor is generally a LOT of work and depending on the type of laser, may require access to fairly sophisticated facilities and equipment (at least compared to the average kitchen sink - and that, too, may be needed!). These may include the need for glass blowing, a high vacuum system, access to a machine shop, and sources for assorted lab supplies, chemicals, pure gases, and specialized optical and electronic components. This is not to say that your dream is unrealistic or impossible - just that one must be quite determined to see such a project through to a successful conclusion and the information in this document will get you started.



Back to Sam's Laser FAQ Table of Contents.

Back to Introduction Sub-TOC.

Back to What is a Laser and How Does It Work? Sub-Table of Contents. Characteristics of Some Common Lasers Here is a summary of the features, power output, power supply requirements, wavelengths, beam quality, cost, and applications of diode, helium-neon, argon/krypton ion, carbon dioxide lasers, helium-cadmium, and solid state lasers. There are many many other types but these represent the most common lasers available over the last 50 years - the the most common lasers available on the surplus market today. Diode lasers. Semiconductor laser diode 'chip' driven by low voltage power supply. Optical feedback from a monitor photodiode (commonly in the same package as the laser diode) is generally used for precise regulation of laser diode current. Wavelengths: Red (635 nm, actually may appear slightly orange-red) through deep Red (670 nm) and beyond, IR (780 nm, 800 nm, 900 nm, 1,550 nm, etc.) up to several um). Near-UV, violet, and blue laser diodes are available from around 380 nm to 450 nm but are still very expensive. Green laser diodes have been produced in various research labs but until recently, only operated at liquid nitrogen temperatures, had very limited lifespans (~100 hours or worse), or both. Beam quality: Fair to high depending on design. The raw beam is elliptical or wedge shaped and astigmatic. Correction requires additional optics (internal or external). Coherence length anywhere from a few mm to many meters. Output power: 0.1 mW to 5 mW (most common), up to 100 W or more available. The highest power units are composed of arrays of laser diodes, not a single device and may exceed 100,000 W. Some applications: CD/DVD players and CDROM/DVDROM drives, LaserDisc, MiniDisc, other optical storage drives; laser printers and laser fax machines; laser pointers; sighting and alignment scopes; measurement equipment; high speed fiber optic and free space communication systems; pump source for other lasers; bar code and UPC scanners; high performance imagers and typesetters, small (mostly) light shows; medical treatment (ophthalmic, uninary, and others). High power laser diodes are the enabling technology for high efficiency Diode Pumped Solid State (DPSS) lasers and future energy efficient lighting. Cost: $1 to $10,000 or more. Comments: Inexpensive, low (input) power, very compact, but critical drive requirements. Many types of diode lasers are not suitable for holography or interferometry where a high degree of coherence and stability are required. However, see the section: Interferometers Using Inexpensive Laser Diodes since these common CD player and visible laser diodes may in fact be much better than is generally assumed. In addition, it has been reported that some inexpensive diode lasers appear to be even superior to traditional helium-neon lasers costing $Ks for holography. See the section: Holography Using Cheap Diode Lasers.

Helium-Neon (HeNe) lasers. Most common are sealed HeNe plasma tube with internal mirrors, high voltage power supply. External mirror HeNe lab lasers also available and expensive. Wavelengths: Red (632.8 nm, actual appearance is actually orange-red) is most common by far. Orange (611.9), yellow (594.1 nm), green (543.5 nm), and IR (1,523.1 nm) HeNe lasers are also readily available (but these are less efficient and therefore more costly for the same beam power). Beam quality: Extremely high. The output is well collimated without external optics and has excellent coherence length (10 cm to several meters or more) and monochromicity. Most small tubes operate with a single spatial/transverse mode (TEM00). Output power: 0.5 to 35 mW (most common), up to 250 mW or more available. Some applications: Industrial alignment and measurement; blood cell counting and analysis); medical positioning and surgical sighting (for higher power lasers); high resolution printing, scanning, and digitization; bar code and UPC scanners, interferometric metrology and velocimetry; non-contact measuring and monitoring; general optics and holography; small to medium size light shows, laser pointers (very rare noawadays but still sort of available), LaserDisc and optical data storage (obsolete, replaced by laser diodes). Cost: $25 to $5,000 or more depending on size, quality, new or surplus. Comments: Inexpensive, components widely available, robust, long life.

Argon (Ar) and krypton (Kr) ion lasers. These differ mainly in gas fill. Sealed plasma tube with internal or external mirrors and high current (10 amps or more at around 100 VDC for the smallest; 50 A at 400 VDC for larger ones) regulated power supply (constant current or optical power based). Combined Ar/Kr produces lines in red, green, and blue, and is therefore considered a 'white light laser'. All are electrical power guzzlers and larger units are water cooled. Wavelengths: Argon ion - Violet-blue (457.9 nm), blue (488 nm - single line), green (514.5 nm); Krypton ion - Green (521 and 532 nm), yellow (568 nm), red (647 nm). Other wavelengths throughout the visible spectrum (and beyond) are available (but generally weaker) and may be 'dialed up' on some models. Mixed gas (Ar/Kr) ion lasers (sometimes called "whitelight" lasers) may produce a combination of both sets of wavelengths. Output power: 10 mW to 10 W. Research lasers up to 100 W. Beam quality: High to very high. Single mode (TEM00) and multimode types available. Some applications: Very high performance printing, copying, typesetting, photoplotting, and image generation; forensic medicine, general and ophthalmic surgery; entertainment; holography; electrooptics research; spectroscopy and other chemical and physics research; and as an optical 'pumping' source for other lasers. Cost: $500 (surplus 100 mW) to $50,000 (multi-watt new) or more. Comments: High performance for someone who is truly serious about either optics experiments like holography or medium to high power light shows.

Carbon dioxide (CO2) lasers. Sealed (small) or flowing gas design. High voltage DC, RF, electron beam or other power supply. Wavelength: Mid-IR. 10.6 um (10,600 nm) is by far the most common but 9.6 um and several other wavelengths are also possible. Beam quality: High. Output power: A few watts to 100 kW or more. Some applications: Industrial metal cutting, welding, heat treatment and annealing; marking of plastics, wood, and composites, and other materials processing, and medicine including surgery. Cost: New systems go for several $K to 100s of $K depending on specific type and output power. Used/surplus low to moderate power (up to 100 W) flowing gas systems may be available for under $500.

Helium-Cadmium (HeCd) lasers. Sealed HeCd plasma tube with internal mirrors, high voltage power supply, and control system. Systems are more complex than other common gas lasers due to the need for control of cadmium vapor pressure and overall temperature/pressure. Actual discharge power requirements are in between HeNe and ion lasers - 1 to 2 kV at around 100 mA. Wavelengths: Violet-blue (442 nm) and ultra-violet (325 nm) depending on the optics. Beam quality: Very high. HeCd lasers usually use sealed narrow bore plasma tubes and operate in TEM00 mode. Output power: 10s to 100s of mW. Some applications: Non-destructive testing and spectroscopy. Cost: High initial cost (many $K) due to low production volume and greater plasma tube and power supply/control system complexity. Older systems may be available for under $100 but almost always need tube replacement or regassing. Comments: Less common than HeNe, Ar/Kr ion, and CO2 types. Few uses for the hobbyist except for the challenge value.

Solid State Lasers. Rod, slab, or disk of crystal or amorphous material usually pumped optically by flashlamps or arc lamps, or high power laser diodes or arrays of laser diodes. Doped optical fiber pumped with high power laser diodes may also be gain medium. The output may be pulsed, CW, or quasi-CW, depending on design and application. Wavelengths: Near-IR (most common are Nd doped materials, around 1,064 nm) to visible (ruby at 694.1 nm), many other materials are now being developed. Output may be frequency multiplied to yield a visible (532 nm) or UV (355 or 266 nm) beam. Output power: Varies widely. Peak in the PetaWatt range (for large research lasers), average up to 1,000 W or more. Q-switching provides extremely high peak power in a short pulse. Beam quality: Low to high. Some applications: Materials processing (drilling, cutting, welding, trimming), green (532 nm) laser pointers and other visible lasers replacing argon ion types, inertial confinement fusion and nuclear bomb research, laser entertainment, laser rangefinders, laser weapons, target designation, medical/surgical, spectroscopy, study of very short pulse phenomena, study of matter, and many many others. For an interactive chart by wavelength of most commercial laser types, go to Laserlookup.com. Positioning your cursor on each laser type/wavelength will display a list of applications as well as a link to suppliers, should you want to buy one. :) The Largest and Smallest Lasers Since you were about to ask: By far the largest pulsed solid state laser on the face of the earth (at least for awhile) will be at the National Ignition Facility being constructed at Lawrence Livermore National Laboratory. It will produce about 1.8 MJ per pulse with a peak output power of over 500 Terawatts. The NIF laser will be about the size of a football STADIUM with 192 beam lines and over 7,300 major optical components including some 3,000 Nd:Glass slab amplifiers nearly a meter across! Its estimated construction cost is more than $1,200,000,000 with an annual operating budget of about $60,000,000. No, the NIF laser isn't portable. And, while its output could in principle be redirected to vaporize mosquitoes, the 192 beam lines presently converge on a microscopic point to implode D-T pellets for fusion research. :-)

The largest CW laser is probably one of the following CO2 lasers: A CO2 laser at the Troisk Institute for Thermonuclear Research (in Troisk, about 80 miles outside of Moscow, Russia) is claimed to be a 10 MegaWatt laser. This is perhaps a slight exaggeration, but not by much. It is truly a CW laser though and would run for as long as power and cooling were supplied. I don't know the exact size of the laser but the room it is in rivaled that of the NOVA laser. A CO2 laser at the Institute of Physics, Savanoriu 231, LT-2053, Vilnius, Lithuania. This laser was so powerful that it had a dedicated electrical power line coming directly from power station.

The smallest lasers in common use are diode lasers like those found in CD players, barcode scanners, and telecommunications equipment. The active region is a fraction of a millimeter long and as little as 1 x 3 micrometer in width and height. The entire semiconductor chip is about the size of a grain of sand. Even smaller 'microlasers' have been developed and some are in commercial production. In principle, a single atom can be the active medium in a laser.



Back to What is a Laser and How Does It Work? Sub-Table of Contents. Lasers for the Hobbyist and Experimenter Why Do People Get Into Lasers? If you are reading this material because you are already a laser nut, skip this section - you already know how you got hooked. For someone who has stumbled upon Sam's Laser FAQ and is wondering why anyone would be interested in such an apparently esoteric topic - or whose only previous contact with lasers has been to tease their pet cat with a laser pointer, here are a few reasons (besides being able to talk about a topic that 99.99% of the World's people haven't a clue about!): Laser technology: - Lasers use all sorts of interesting electronics, optics, and mechanics. Much of this involves complex circuits, high quality mirrors, precision structures, and other high tech toys. Skills needed to deal with laser design, adjustment, testing, and repair may include high voltage electronics to vacuum systems and gas handling; pulsed high energy discharge circuits; stable DC or RF current or voltage sources, drivers, and modulators; structural components like optics mounts and resonators; and much more. A working laser is a study in technological beauty. This is my main interest. :)

- Lasers use all sorts of interesting electronics, optics, and mechanics. Much of this involves complex circuits, high quality mirrors, precision structures, and other high tech toys. Skills needed to deal with laser design, adjustment, testing, and repair may include high voltage electronics to vacuum systems and gas handling; pulsed high energy discharge circuits; stable DC or RF current or voltage sources, drivers, and modulators; structural components like optics mounts and resonators; and much more. A working laser is a study in technological beauty. This is my main interest. :) Laser applications: - There are literally 10s of thousands of uses for lasers using devices ranging from the microscopic laser diode in a CD or DVD player to huge industrial carbon dioxide lasers for cutting, welding, and other large scale materials processing. However, the most common application of lasers for fun would be to create the dynamically changing patterns and graphics of a laser light shows using a combination of helium-neon, argon and krypton ion, arc lamp or diode pumped solid state, and diode lasers, along with modulators and deflectors.

- There are literally 10s of thousands of uses for lasers using devices ranging from the microscopic laser diode in a CD or DVD player to huge industrial carbon dioxide lasers for cutting, welding, and other large scale materials processing. However, the most common application of lasers for fun would be to create the dynamically changing patterns and graphics of a laser light shows using a combination of helium-neon, argon and krypton ion, arc lamp or diode pumped solid state, and diode lasers, along with modulators and deflectors. Laser research: - The laser is a wonderfully sophisticated but in many ways, elegantly simple device that makes use of the fundamental principles of quantum mechanics. There are vast uncharted waters to be explored (no, this is not about sailboats!) in creating new and more advanced types of lasers and systems using lasers. While the typical experimenter and hobbyist isn't likely to have access to the types of facilities and equipment to discover anything fundamentally new, they can keep up with much of the developments through trade magazines and scientific literature. If you are now thinking: "I'd probably enjoy bamboo under the fingernails or root canal therapy more than any of this", perhaps lasers aren't for you. ;) However, if anything you have read so far seems fascinating or really way cool, then continue on. It doesn't take a lot of money to get into lasers ($10 will get you a laser and a simple laser show can be put together for under $25 - though it is quite possible to end up spending many $1,000s even on used or surplus lasers and laser related equipment!) but it does take a driving interest and the ability and willingness to construct and tinker. If you are incapable of changing a light bulb without the instruction manual, perhaps lasers aren't for you either. Lasers are also not the sort of thing where you are likely to find many other people in your immediate neighborhood sharing your passion except in a few places - mostly near laser manufacturers or research installations. So, be prepared to do most of your interaction via the Internet and other long distance correspondence. There are few laser clubs and no laser trading cards (but trading of laser equipment is quite popular)! Having said all that, doing almost anything successfully with lasers can be very rewarding and if you haven't decided on a career, could give you a head start in the photonics area - the merging of lasers, optics, and electronics - which is one of the key technologies of today and the future. (From: Bob.) If you are still in high school, and you REALLY want to get into lasers your choices for college would be University of Rochester, followed by a coin flip decision between University of Arizona or University of Central Florida. Also there are numerous other schools with some optics courses and laser research. Commercial Lasers Versus Amateur Laser Construction Diode, helium-neon (HeNe), argon/krypton (Ar/Kr) ion, and Diode Pumped Solid State (DPSS) lasers are probably the most popular types of lasers generally available to hobbyists and experimenter (see the section: Characteristics of Some Common Lasers). This is due to the wide availability of complete lasers and laser components (new as well as surplus), and their desirable optical and physical characteristics, including the generation (in most cases) of a continuous beam, manageable power and cooling requirements, and the fact that there is no need for sophisticated laboratory facilities to keep them healthy. A major portion of this document is devoted to the practical aspects of these types of laser systems, their power sources, and related optics and electronics. Of these, I still consider the HeNe laser to be the quintessential laser: An electrically excited gas between a pair of mirrors. It is also the ideal first laser for the experimenter and hobbyist. OK, well, maybe after you get over the excitement of your first laser pointer! :) HeNe's are simple in principle though complex to manufacture, the beam quality is excellent - better than anything else available at a similar price. When properly powered and reasonable precautions are taken, they are relatively safe if the power output is under 5 mW. And such a laser can be easily used for many applications. With a bare HeNe laser tube, you can even look inside while it is in operation and see what is going on. Well, OK, with just a wee bit of imagination! :) This really isn't possible with diode or solid state lasers. While many other types of lasers may be acquired or constructed including: mercury vapor ion, nitrogen, excimer, dye, ruby, Nd/YAG, chemical, free electron, and X-ray, most of these are less commonly available as surplus. There could also be problems obtaining the 100 million volt particle accelerator required for the free electron laser and the small thermonuclear device needed to pump the X-ray laser. :-) Now, back down to earth.... Where you are really interested in actually constructing any of these types of lasers from basic materials (e.g., not by simply hooking together commercial laser tubes and power supplies), check out the chapters beginning with: Amateur Laser Construction which include general information on the types and requirements for home-built lasers, setting up a laser lab, introduction to vacuum systems and glass working, and other really exciting topics. General Comments on Lasers as a Hobby (From: Richard Alexander (RAlexan290@gnn.com).) How much do you like to build things? Would you prefer to assemble a bunch of parts, or do you want to blow your own glass tubes, too? Do you have any mechanical experience? Do you build electronic kits? Keep in mind that you will often be working with intense light (enough to instantly damage your unprotected eyes, and maybe your unprotected skin) and high voltages. All laser experimenters (and optics types, too) should have a copy of "Scientific American"'s "Light and Its Uses." [5] It gives construction plans for a Helium-Neon (you blow the glass tube yourself), an argon ion (even more complicated), a CO2 (designed and built by a high school student, and able to cut through metal), a dye, a nitrogen (a great first laser, but watch out for UV light) and a diode laser (obviously, you buy the diode laser and assemble the driver circuit from the plans they supply). They also explain how to make holograms using visible and infrared light, microwaves and sound. There are other projects, too. The book is getting fairly old (the HeNe dates to the '60s), but it's still a great reference. A nitrogen laser may be built for under $200 (maybe less than half that amount if you are lucky). It requires no mirror alignment (since it has no mirrors). The technology for building this laser was available to Ben Franklin, so there is nothing too critical in it. The hazards it presents are lots of ultraviolet light (spark discharges and laser beam), high voltage (necessary to arc across a 1/4 inch spark gap in a nitrogen environment) and circuit etcher (the main capacitor is made from an etched circuit board). Once built, the nitrogen laser can drive many other projects. It can be used as a pump for the dye laser, for example. It will light up anything fluorescent. It is a pulse laser (10 ns) that can be repetitively pulsed (120 Hz is a likely frequency). Megawatt power is possible, but the total energy is low (due to the short pulses). Helium-Neon laser tubes may be bought from many mail-order companies. I bought one from Meredith Instruments in Arizona. They cost about $15, and the power supply can be built or bought for about another $20. You have the option of buying tubes with mirrors attached or not. You might want to buy the mirrors attached, because aligning those mirrors is extremely tedious. I was given an "A" for constructing a working Helium-Neon laser from the parts in the Laser Lab in less than an hour. The class was given two semesters to gain the experience they needed to do that. If you want more than one color from lasers, there are various ways to do it, but none of them are as nice as one might like. For $3,000 or so, you can buy a Helium-Neon laser that will produce laser light ranging from infra-red to green. All you have to do is turn a dial on the back. But it's very low power (a few mW) and not really very useful to the hobbyiest except as an expensive conversation piece. :) Laser light shows usually use argon ion or krypton lasers and/or arc lamp or diode pumped solid state laser. The ion lasers are able to produce most of the colors of visible light, and some can also be dialed to the desired color. The solid state lasers are most often green but other colors are becoming available. However, professional quality laser systems usually cost many thousand dollars ($40,000 is not too unusual) and require either forced air or water cooling or a combination. A dye laser is the usual solution to the multi-color problem. They are inexpensive and simple. They aren't especially tunable, unless you change the dye, although a diffraction grating can be used to tune a particular dye to various colors. One common dye that can be used in a dye laser is the green dye found in radiator antifreeze. Database of Equipment Containing Interesting Lasers We all know that CD, DVD, MiniDisc, LaserDisc, and other optical storage devices; barcode scanners, laser printers, laser pointers, and so forth, contain lasers but all sorts of other equipment does as well. And, some of those lasers may be nice and large and powerful. Each of the respective chapters on particular types of lasers has information on their common uses and in some cases, specific models of equipment where they may be found (mostly argon ion). Mike Harrison (mike@whitewing.co.uk) has a Web page in the early stages of development which lists graphic arts, industrial, medical, scientific, and other equipment which include internal lasers of all kinds. The page can be updated with your contributions as well. Take the link near the bottom of Mike's Electric Stuff Page (which also has a lot of other interesting topics).



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