Sam's Laser FAQ, Copyright © 1994-2005, Samuel M. Goldwasser, All Rights Reserved.
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    Home-Built Laser Types, Information, and Links

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    Introduction to Descriptions and Designs of Home-Built Lasers

    What is in this Chapter?

    Having survived a discussion of lab/workshop safety and requirements, vacuum systems, glass working, optics, and power supplies, it is now time to look into the detailed features and characteristics of the types of the lasers that are possible to construct at home. This chapter is a sort of introduction to the detailed chapters on each of the lasers that follow. In addition, there are some comments later on that may be of help in deciding which home-built laser to tackle first (or second or third). At the end of this chapter is information on the Scientific American (SciAm) laser articles including the collection: "Light and its Uses" and possible on-line access to this valuable resource.

    Each of the chapters that follow are dedicated to one particular type of home-built laser. For most, it is one of those presented in Scientific American which is first summarized, followed by any non-SciAm designs, and other related information. There may also be other projects specifically related to each type of laser. Some of these (like the ones on the HeNe laser in particular), may require much less custom work by using more off-the-shelf new or surplus parts and are thus alternatives to diving into a fully home-built design.

    Note that the ORDER of the first 7 of the following chapters is based on the sequence in which these lasers were presented in Scientific American and does NOT reflect their level of difficulty! For that, please see the comments starting in the section: Which Laser to Build? and the more specific information in each chapter.

    In the chapter for each type of home-built laser, information directly related to the relevant SciAm laser (where applicable) will be presented roughly as follows (not all of these items will be present for every laser):

    1. Introduction and general description.

    2. Specific laser output, electrical, and other safety information.

    3. Links to relevant Web sites with additional information including some that offer kits, plans, or even completed lasers (don't whimp out on me!).

    4. Photos or links to photos of completed home-built lasers.

    5. Diagrams showing major mechanical and electronic assemblies of typical home-built lasers.

    6. Summary of the major optical, physical, and electrical, characteristics and requirements, including an estimated 'level of difficulty' profile. See the section: Home-Built Laser Description.

    7. Sources for parts and supplies relevant to each particular type of home-built laser.

    8. Guidelines for improving the chances of a successful outcome for construction of those lasers that are finicky about their design or fabrication and which shouldn't be modified (except as noted) until the basic version is happily lasing.

    9. Any errata, suggestions, improvements, or other information that might simplify construction, alignment, enhance reliability, or boost power output, as well as identifying any special safety considerations.

    10. Email correspondance with those who have attempted their construction possibly including additional complete laser descriptions as in (4), above.

    11. Articles, newsgroup, and discussion group postings relating to the particular type of home-built laser. Where the same type of laser (e.g., HeNe, Ar/Kr ion, CO2) is covered in Part III of this document, those chapters should be read FIRST since the basic characteristics and principles of operation are described there.

      Home-Built Laser Description

      Each of the following chapters include a description of the corresponding laser from the Amateur Scientist article of Scientific American (or the collection "Light and its Uses") if one exists. This will include a somewhat standardized summary of the most important physical, electrical, and optical characteristics of the laser including the resonator, and necessary power supply, and vacuum system or other special requirements. An estimate of the required skills and level of difficulty for each will also be provided.

      The format of the laser specifications will follow the general outline given below. (Since most of these are gas lasers many of the entries will be missing for the dye laser and solid state lasers.)

      • Level of difficulty (rated L=low, M=medium, H=high):

        • Glass work (if any).
        • Fabrication (other than glass work).
        • Vacuum/gas handling.
        • Power supply.
        • Additional apparatus (optics, alignment jig, etc.)
        • Risks (high voltage, toxic chemicals, etc.).

      • Lasing wavelength(s) - Output wavelengths which are obtainable with the design as described as well as possible others that may be produced with straightforward modifications.

      • Resonator:

        • Type/lasing medium (gas, solid, liquid). All but one of these (the dye laser) use gas or vapors from sublimation or heating of a liquid or solid as the lasing medium.

        • Bore diameter (ID/OD), bore length (millimeters/inches). The bore is the actual location where lasing action is supposed to take place in a gas laser. It may also be called the 'capillary'. While the overall laser tube may be much larger, and the electrical discharge is usually not confined to the bore, for all intents and purposes, one can assume that only the lasing medium inside the bore participates in stimulated emission because the discharge is usually much more concentrated there.

        • Total tube length - includes additional space beyond the actual bore (e.g., to the center of the Brewster windows).

        • Tube material - glass (soda-lime or borosilicate), Plexiglas, etc.

        • Electrodes (type, materials, construction) - All of these gas lasers use some variation of a cold cathode design.

        • Gas fill (Gases, pressure/range, purity) - This will include pressures or partial pressures and molar/volume ratios.

        • Cooling (convection air, forced air, water) - All are convection air cooled except for the CO2 which is water cooled. Adding water cooling to the others like the argon ion laser may permit their output power to be boosted.

        • Coupling (internal mirrors, Brewster windows, etc.).

        • Mirrors (HR/OC, coating, figure/shape, reflectance, mounts, alignment). Most are dielectric type, either planar or confocal concave. Mirror mounts. RoC denotes Radius of Curvature; R denotes reflectance (usually at a specified wavelength or range of wavelengths).

        • Total resonator length (mirror to mirror).

        • Vacuum system:

        • Requirements - low-medium (e.g., N2 laser, dye laser flashlamp) or medium (most others).

        • Sealed/flowing - All can be sealed to some extent though the lifetime of these home-made laser tubes is not that long. Thus, some means of regassing without glass work is desirable. The CO2 probably requires a flowing gas design.

      • Special chemicals/supplies required (other than gases).

      • Excitation/Pumping:

        • Type (electrical/optical) - All the gas lasers are pumped electrically; the dye laser uses a flashlamp.

        • Power supply (DC/AC/RF, pulse, voltage/current/power/frequency, regulation).

        The following notation will be used to denote input and output connections:

        • G = AC line safety (earth) Ground.
        • H = AC line Hot.
        • N = AC line Neutral.

        • HV AC = the output of AC power supplies.
        • HV+ (or similar) = a positive output of DC power supplies but prior to any ballast resistor or special pulser.
        • HV- = the negative return for DC power supplies.
      The beauty of a home-built laser is that there is no law that says you cannot experiment with virtually all of these specifications. If you want to build a HeNe laser with a longer or narrower bore or with a large 'can' style cold cathode instead of a neon sign electrode - go for it! Boosting power output, in particular, may be quite viable especially for the pulsed lasers like the Ar ion and CuCl/CuBr with a more sophisticated power supply and additional (e.g., water) cooling.

      Duplicating (or improving on) a known commercial design rather than one from a 20+ year old article could very well result in higher efficiency and output power and better beam quality. See the section: Sam's Three Part Process for Getting Your Feet Wet in Gas Lasers for one possible approach to this.

      Which Laser to Build?

      A variety of factors should be considered in determining which of the many possible lasers to undertake. In addition to difficulty, there are other personal factors such as the desire for a visible CW or pulsed beam or high enough power to be used for wood or metal working (e.g., CO2 or ruby/Nd:YAG).
      • Although the helium-neon (HeNe) and argon/krypton (Ar/Kr) ion lasers are relatively simple in basic structure, they have some of the most stringent requirements on vacuum, gas purity and the need to minimize contaminants in the tube and vacuum system, and the need for precise pressure control. I would also advise against the copper chloride and copper bromide lasers since they are more complex in a couple of areas (the need for a heater and the double pulse power supply).

      • Carbon dioxide (CO2) lasers really want to work - there is a wide variation of design, operating pressure, gas fill, and power supply that will result in a functioning laser (even if not quite optimal). The beam is high power but invisible.

      • A nice compromise might be had in the Pulsed Multiple Gas (PMG) laser since it can use a variety of gases and operates flowing gas mode which simplifies the vacuum requirements.

      • The helium-mercury (HeHg) laser is another one that is relatively easy in terms of glass working, vacuum system, chemicals, and power supply requirements.

      • The nitrogen (N2) laser is probably the easiest to build, can be used to pump the dye laser, and has minimal risks. So, one could build the N2 laser and then the dye laser and compare pumping methods! But, like that of the CO2 laser, its beam is invisible - UV in this case. It is also not very well collimated so optical manipulations are problematic.

      • Although the Pulsed Solid State (PSS) and Diode Pumped Solid State (DPSS) laser may not quite have the attractive quality of being a truly from scratch project as is the case with the other home-built lasers, both types have their desirable attributes: a home-built PSS laser can easily produce hole blasting energy and a home-built DPSS laser with a frequency doubling crystal can produce the highest power visible (green) CW beam of any home-built laser.

      (From: Flavio Spedalieri (fspedalieri@nightlase.com.au).)

      My opinion and that of many other laser experimenters is that the home construction of Ar/Krypton and HeNe lasers, requires much more critical control, and generally it may lead to a laser that will never produce a beam (but the educational experience is very valuable).

      Also, Argon and Helium Neon lasers are very cheap, and quite common, so when you compare the construction of these lasers with the purchasing them from surplus market, its more cost effective to just purchase a commercial argon ion or HeNe laser tube (and build your own resonator and power supply if you like).

      I would suggest building a laser that is not as readily available, and the cost of such systems are very high - it's a great feeling to have built a laser that is worth tens of thousands of dollars, yet only have spent a few hundred dollars.

      The lasers that are a good for construction are:

      • Copper Vapor - Nice yellow/green output - output powers in the range of 10 watts or more. (The copper halide lasers are easier to build though).

      • Mercury Vapor - Blue Output, quit easy to build, but cavity optics can be a problem. Although argon or 'white light' ion optics may be usable, obtaining these of sufficient diameter for the wide bore will be expensive unless you get lucky.

      • Carbon Dioxide - The workhorse of lasers - very easy to build, high power. Variations on the cavity design also can be a good challenging project.

      • Nitrogen Laser - Very easy to build, High Power UV pulses great for pumping a dye laser.

      • Dye Laser - Fairly easy to build, tunable across many colours.

      • Ruby Laser - The laser that started it all - deep red output, able to be Q-switched, high power, pulses.

      • Nd:YAG - Similar to the ruby, can be frequency doubled into the green spectrum (532 nm) and can be pumped by high power laser diodes.
      These are just some of the possible lasers that can be built by the dedicated laser experimenter.

      Can I Use the Same Tube for Multiple Home-Built Lasers?

      There is a great amount of similarity between some of the home-built lasers described in subsequent chapters as well as with variations on these which aren't dealt with explicitly (e.g., HeHg and HeCd).

      However, there are enough differences that for most of these home-built lasers, it doesn't make sense to do this. Even between, say the HeNe and Ar/Kr ion lasers, the Brewster angle and bore diameters differ somewhat. The CO2 laser uses a wide bore and internal mirrors while the HeHg uses a wide bore but external mirrors. The electrode requirements differ as well. Finally, some of the materials - like mercury - will contaminate the glass and metal parts of the tube and vacuum system so attempting to reuse a tube with a different gas-fill may be counterproductive. However, if you really want to try it, see the section: Comments on a Universal Experimenter's Gas Laser.

      Here are some additional comments specifically for the CO2 laser versus the others:

      (From: Flavio Spedalieri (fspedalieri@nightlase.com.au).)

      Unfortunately, it is not possible to use the same tube for the CO2 and HeNe or argon/krypton ion lasers:

      • Flowing gas CO2 lasers use a large diameter bore typically 10 to 20 mm.
      • Argon/krypton ion and HeNe lasers use fine diameter bores in the vicinity of 0.5 - 1.5 mm.
      Also these lasers are much more critical in the following areas:
      • Vacuum - A decent vacuum system is required, typically a 2 stage rotary vain pump is used as a roughing pump, with second diffusion pump to remove air that the rotary pump will not. In all cases ANY residual air left in the laser tube is detrimental to laser operation - it is also a major cause for the laser not to work

      • Gas fill - The Gas used in these lasers must be very pure - in the vicinity of 99.999% pure - again, any traces of contaminants in the gas is detrimental.

      • Gas Pressure; Gas pressure in these lasers must also be precisely controlled.

      Estimate of Home-Built Laser Output Power

      None of the articles in "Light and its Uses" ever list the output power of the home-built lasers. This isn't surprising given the era (1960s for this one) and even the present high cost of laser power meters (see the section: What Makes a Laser Power Meter So Expensive?.

      Where possible, an attempt will be made to estimate the expected power (or at least an upper bound) based on tube dimensions, power supply, and other factors. At best this will be a wild guess but may provide some indication of the possibilities for improvement by tweaking the design.

      Note that this also means that it is NOT possible to determine the laser safety classification for these lasers. They maybe of very low power but this is not guaranteed. So, treat their output as at least Class IIIb (Class IV for the CO2 laser) until you can be sure that it isn't!

      So, Maybe Constructing a Laser from Basic Elements Isn't for You?

      If you're still not sure which laser to build - or whether building a laser from scratch is for you at all, consider using a commercial HeNe or argon ion tube with one or two Brewster windows and constructing a resonator including mirror mounts. This will give you a feel as to whether dealing with metalworking and precision optics is something you enjoy without having to invest in a vacuum system, and obtain weird gases and other supplies. The power supply can be built or bought as desired. You will still have to fight with mirror alignment and can gain access to the inside of the laser cavity for experiments And, perhaps most important, you can really impress your friends with a way-cool high-tech looking laser. :)

      I would definitely recommend the HeNe over the argon ion laser tube as it is a lot easier and cheaper to build or buy a suitable power supply - and somewhat safer as well. Somehow, working around high voltage but low current of a HeNe laser just seems to me to be much less scary than being in close proximity to the non-isolated AC line voltage at many amps (and killer fan) of an ion laser!

      A little searching of the laser surplus places should turn up an inexpensive HeNe laser tube of this type (you may have to ask explicitly - they never seem to be in the catalogs but usually lurk on a forgotten shelf in a rear storage room on the second level sub-basement. :)

      See the sections starting with: The Half-Way Approach for a Home-Built HeNe Laser and A One-Brewster HeNe Laser Tube.

      There are other alternatives in between this approach and a full-blown from beach sand up laser project. See the additional information in the chapters on the home-built HeNe and Ar/Kr ion lasers.

      Solid state lasers are inherently of the "half-way approach" type since you can't grow, shape, grind, and polish your own laser crystals; or build flashlamps or laser diodes. Yet, they have many attractive qualities. Pulsed SS lasers can generate the highest pulsed power of any home-built laser and diode pumped SS lasers have the ability to generate high green CW power. Parts are becoming more readily available at attractive prices and with reasonable precautions and awareness of the safety issues, the risks are relatively low and the chances of a successful outcome are quite high.



    12. Back to Home-Built Lasers Types, Information, and Links Sub-Table of Contents.

      Scientific American Articles on Lasers and Related Topics

      The laser construction articles from the Scientific American "Amateur Scientist" columns (most of which were subsequently reprinted in the collection "Light and its Uses") still represent the best source of information of its type available to the hobbyist and experimenter. While research and technical papers may exist on these topics, access to them is often non-existent to common people and/or they are written at such a level as to be of minimal value to anyone who isn't an expert in the field.

      Here is a list of some of the laser articles that have been published in the Amateur Scientist columns of Scientific American. The first 7 of these constitute the chapters on laser construction found in "Light and its Uses":

      1. Helium-Neon Laser, September, 1964, pg. 227.
      2. More on the Helium-Neon Laser, December, 1965, pg. 106.
      3. Argon Ion Laser, February, 1969, pg. 118.
      4. Tunable Dye Laser, February, 1970, pg. 116.
      5. Carbon Dioxide Laser, September, 1971, pg. 218.
      6. Infrared Diode Laser, March, 1973, pg. 114.
      7. Nitrogen Laser, June, 1974, pg. 122.
      8. Mercury-Vapor Ion Laser, October, 1980, pg. 204.
      9. Copper Chloride Laser, April, 1990, pg. 114.

      Except for the one in (6) which for all practical purposes you can ignore, all the others are built from the ground up using basic materials like glass tubing, pieces of plastic and metal, mirrors and other optics, glue, duct tape, various bottled gases and other chemical supplies, high voltage transformers, resistors, capacitors, diodes, wire, etc., along with blood, sweat, and possibly some tears. :) (The article in (6) deals with driving a long obsolete type of IR laser diode which had limited applications. However, modern equivalents do still exist. See the section: And Those High Power Pulsed Laser Diodes? if interested.)

      In addition to actual laser construction, there have also been related articles on vacuum systems, glass working, and other laser related subjects, particularly during the initial laser craze of the 1960s and 1970s but extending to the present particularly for more exotic types of lasers and laser applications including holography and interferometry.

      As an aside, I lament the fact that few of the more recent Amateur Scientist columns have nearly as much sophistication and depth as those from that era. On the other hand, experiments that are presented may be performed by nearly anyone who is reasonably handy using parts from the local home center and Radio Shack and yet this is definitely real science. There is no need for high vacuum systems, glass working skills, strange gas mixtures and other chemicals, or fancy test equipment!

      A large public or university library will likely have all of these somewhere though you may have to request them from their storage vaults and/or they may be on microfilm or microfiche. While the Scientific American Web site has many interesting articles, they do not go far enough back to be of much use for laser construction. For possible Web access, see the section: On-Line Access to the Scientific American Laser Articles.

      There are a couple of Web sites to find complete indexes to the Amateur Scientist articles from 1952 to the present. That should be far enough back to be good enough for anything laser related! One is Amateur Scientist Index in K3PGP Experimenter's Corner.

      Or, specifically for laser construction and optics articles, see the sections: Light and its Uses - Complete Table of Contents. However, the more general indexes may be more useful since they also list project articles in related fields like vacuum systems and electronics. The book "Light and its Uses" is long out of print but your library may have this as well (in its ancient not-that-popular books collection!). It may also be possible to obtain a copy from a dealer in used scientific books. Although Internet companies like Amazon.com offer to attempt to find such books, going to a more specialized search site like: Bibliofind (which appears to be owned by Amazon.com now) may be more productive. They claim to have access to "ten million used and rare books, periodicals and ephemera offered for sale by thousands of booksellers around the world". I have heard of this being a successful means of obtaining "Light and its Uses".

      On-Line Access to the Scientific American Laser Articles

      In the age of electronic access, it would obviously be desirable to be able to browse articles from Scientific American on-line. While the Scientific American Web site has many interesting articles, they do not go far enough back to be of much use for laser construction and apparently have little interest in out-of-print material. I have attempted to obtain permission from Scientific American to provide the chapters on laser construction in "Light and its Uses" on-line. Unfortunately, the editors of Scientific American have denied my request. I had even offered to scan and OCR the originals and have Scientific American maintain the resulting documents SOLELY at THEIR Web site - yet they still refused! "For policy reasons", they said. Probably too many layers :-(. Since I will not knowingly violate someone else's copyright, that's as far as it goes - here. > That's the bad news.

      The good news is that Chris Favreau (cfavreau@hotmail.com) has begun to upload the laser constructions articles from Scientific American - I just hope the SciAm police don't get wind of it. :) These appear to be exactly what I wanted to do originally - OCRed or transcribed text and scanned graphics in efficiently compact HTML and .gif format, respectively. So, check out Chris's Mad Scientist Page.

      CDROM with the SciAm Amateur Scientist Archive

      The Society of Amateur Scientists (SAS) now has the CDROM of the entire 70 year run of Scientific American's "The Amateur Scientist" column. This is your chance to obtain everything on lasers from "Light and its Uses" as well as the articles that followed, vacuum systems, high voltage, and much much more. A CDROM is now available with all of the articles since the 1920s scanned, OCR'd and converted to HTML, complete with thumbnails and high resolution images of the illustrations.

      Check out their Tinker's Guild website:

      The CDROM is now available and priced at $89.95 from Tinkers Guild but only $79.00 from Surplus Shack (I don't know how long that price will last though).

      Light and its Uses - Complete Table of Contents

      Even after more than 20 years, "Light and its Uses" is considered to be THE reference for amateur laser construction. However, it is easy to overlook the many other excellent projects contained in this work. They are probably of even more value overall because fabrication of most of the optical instruments is less demanding in some ways than the lasers since no vacuums, or messy or toxic chemicals are required and light sources and readily available low cost lasers other than those from the construction articles can be used.

      LIGHT AND ITS USES:

    13. MAKING AND USING LASERS
    14. HOLOGRAMS
    15. INTERFEROMETERS
    16. INSTRUMENTS OF DISPERSION

      THE AMATEUR SCIENTIST

      Readings from: SCIENTIFIC AMERICAN

      Introductions by: Jearl Walker, Cleveland State University

      Publisher: W. H. Freeman and Company, San Francisco

       
      CONTENTS
      

      I. LASERS

      Introduction 3

      1. Helium-Neon Laser (Sep, 1964) 7 A helium-neon laser built in the home by an amateur

      2. More on the Helium-Neon Laser (Dec, 1965) 14 Increasing the life of the amplifier tube at modest cost NOTE ON CLEANING THE MIRRORS 17

      3. Argon Ion Laser (Feb, 1969) 18 An argon gas laser with outputs at several wavelengths

      4. Tunable Dye Laser (Feb, 1970) 24 An inexpensive tunable laser made at home using organic dye NOTE ON THE POWER CIRCUIT 29 April 1970

      5. Carbon Dioxide Laser (Sep, 1971) 30 A carbon dioxide laser constructed by a high school student

      6. Infrared Diode Laser (Mar, 1973) 35 A solid-state laser made from semiconducting materials

      7. Nitrogen Laser (Jun, 1974) 40 An unusual gas laser that puts out pulses in the ultraviolet NOTE ON EXTRACTING NITROGEN FROM AIR (Oct, 1974) 44

      II. HOLOGRAMS

      Introduction 46

      8. Homemade Hologram (Feb, 1967) 43 Experimenting with homemade and ready-made holograms

      9. Stability of the Apparatus (Jul, 1971) 55 Insuring a good hologram by controlling vibration and exposure

      10. Holograms with Sound and Radio Waves (Nov, 1972) 57 Sound and radio waves recorded on film by a precooling process

      III. INTERFEROMETERS

      Introduction 61

      11. Michelson Interferometer (Nov, 1956) 66 A homemade instrument that can measure a light wave

      12. Cyclic Interferometer (Feb, 1973) 70 An interferometer constructed from plate glass and lenses

      13. Speckle Interferometer (Feb, 1972) 72 A laser interferometer that can measure displacement 14. Series Interferometer (June, 1964) 76 A series interferometer to observe various subtle phenomena

      15. Interferometer to Measure Velocity (Dec, 1965) 81 A laser interferometer that converts a velocity to a sound signal

      16. Interferometer to Measure Dirt Content of Water (Jun, 1973) 82 A laser beam and a photocell to measure the dirt content of water IV. INSTRUMENTS OF DISPERSION

      Introduction 88

      17. Ocular Spectroscope (Dec, 1952) 90 A spectroscope for a telescope that separates colors in starlight

      18. Bunsen Spectroscope (Jun, 1955) 92 Reconstructing the spectroscope that initiated modern spectroscopy NOTE ON MAKING LIQUID PRISMS (Apr, 1956) 95

      19. Diffraction-Grating Spectrograph (Sep, 1956) 96 An inexpensive diffraction-grating spectrograph

      20. Diffraction-Grating Spectrograph to Observe Auroras (Jan, 1961) 102 Auroral spectra made as part of the International Geophysical Year

      21. Inexpensive Diffraction-Grating Spectrograph (Sep, 1966) 106 A spectrograph with the grating mounted on a concave mirror NOTE ON THE GRATING (Nov, 1966) 111

      22. Ultraviolet Spectrograph (Oct, 1968) 112 A spectrograph with a quartz prism for work in the ultraviolet

      23. Inexpensive Spectrophotometer (May, 1968) 118 A photocell to measure the intensity of color transmitted by a liquid

      24. Recording Spectrophotometer (Jan, 1975) 124 A recording spectrophotometer built by a high school student

      25. Spectroheliograph (Apr, 1958) 131 A spectroheliograph to observe details on the disk of the sun

      26. Spectrohelioscope (Mar, 1974) 136 A new kind of spectrohelioscope to observe solar prominences Bibliographies 143

      Index 145



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      Sam's Laser FAQ, Copyright © 1994-2005, Samuel M. Goldwasser, All Rights Reserved.
      I may be contacted via the Sci.Electronics.Repair FAQ Email Links Page.