A Brief History of Laser Epilation

A Brief Introduction to Lasers Principles and Structure
The Laser Age
Since every document on lasers must have a discussion of basic principles, this is it! If you know anything at all about lasers, you can skip to the section: Characteristics of Some Common Lasers since the summary below will probably just put you to sleep and then you might miss the rest of the excitement. :-) If you want a more in-depth on-line course, see the section: On-Line Introductions to Lasers.
A laser is a source of light but unlike anything that had ever been seen or implemented before 1960 when Theodore H. Maiman of Hughes Aircraft mounted a specially prepared synthetic ruby rod inside a powerful flash lamp similar to the type used for high speed photography. (If you're into reading heavy scientific literature, the reference is: T. H. Maiman, "Stimulated Optical Radiation in Ruby", Nature, 6 Aug. 1960, vol. 187, no. 4736, pgs. 493-4.) When his flash lamp was activated, an intense pulse of red light burst forth from the end of the rod that was both monochromatic (a single color) and coherent (all of the waves were precisely in step). The difference between the output of a laser and that of an incandescent light bulb is like the difference between white noise and a single tone.

The laser age was born. Within a very short time, in addition to many more solid state materials, laser action was demonstrated in gasses (the ubiquitous helium-neon laser was the first gas laser though it originally only produced invisible IR wavelengths), liquids, and semiconductor crystals. Almost every conceivable material was tried in the frenzy to produce new and interesting lasers. Even some varieties of Jello(tm) brand dessert were blasted with xenon light, and according to this legend, are supposed to work fairly well. I wonder whether the flavors have to be all natural. :-) (See the section: Comments on the Jello Laser Legend for a discussion on this very exciting topic.)

See Laser Stars - LASER HISTORY (1917-1996) for an interesting chronology of laser development, discovery, and applications.

Although the first working laser was built at Hughes Aircraft, much of the early theoretical and practical work was done at Bell Labs - work which continues till the present day. See The Invention of the Laser at Bell Labs: 1958 - 1998. Quoting from this site:

"The invention of the laser, which stands for light amplification by stimulated emission of radiation, can be dated to 1958 with the publication of the scientific paper, Infrared and Optical Masers, by Arthur L. Schawlow, then a Bell Labs researcher, and Charles H. Townes, a consultant to Bell Labs. That paper, published in Physical Review, the journal of the American Physical Society, launched a new scientific field and opened the door to a multibillion-dollar industry."
In many ways, the laser was a solution looking for a problem. Well, the problems soon followed in huge numbers. It would be hard to imagine the modern world without lasers - used in everything from CD players and laser printers, fiber-optic and free-space communications, industrial cutting and welding, medical and surgical treatment, holography and light shows, basic scientific investigation in dozens of fields, industrial cutting and welding, and fusion power and Star Wars weapons research. The unique characterisics of laser light - monochromicity (the light is very nearly a single wavelength or color), coherence (all the waves are in step), and directionality (the beam is either well collimated to start or can easily be collimated or otherwise manipulated) make these and numerous other applications possible. In fact, it is safe to say that the vast majority of laser applications have not yet even been contemplated. For an idea of the extensive and diversified applications for which the laser has become an essential tool or component, see for example: Rami Arieli - The Laser Adventure: Laser Applications and Lasers On-Line: Some Applications.

On-Line Introductions to Lasers
There are a number of Web sites with laser information and tutorials. Many are of marginal value at best. However, there are a few that stand out as being well worth bookmarking:
The best that I have found by far is the Laser/Electro-Optics Technology Series being developed by CORD Communications, 324 Kelly Drive, P.O. Box 21206, Waco, Texas 76702-1206. This is essentially a complete on-line textbook with over 100 diagrams, many basic equations (you can't have everything!), detailed laboratory experiments, and extensive lists of references for further study.
There are several (mostly complete) courses (some are still under development and there are a few rough edges). While the original material was developed in the early 1970s (there are a number of diagrams with tube circuits!), it has been updated and has a lot to offer including by far the most complete on-line presentation of laser technology (e.g., resonator structures and power supply example schematics) that I know of - though not to the level of detail present in Sam's Laser FAQ! :)

The blurb that goes along with the courses states:

"The LEOT (Laser/Electro-Optics Technology) curriculum was developed by CORD in 1970-1974 with funding from the U.S. Office of Education. At that time many books on lasers were available for physicists and engineers. Those books contained the rigorous theoretical information needed to develop new designs and applications for lasers. The LEOT curriculum does not provide that kind of information, but instead, is written for the technicians who will build, modify, install, operate, troubleshoot, and repair lasers.
Technicians are a vital link in the advancement of photonics technology. They are the workers in the laboratories, plants, and fields who ensure that lasers, and other photonics related equipment, operate properly and reliably."

So these course are very practical in nature and provide a nice companion to Sam's Laser FAQ's practical orientation.

(Note: As of Summer, 2001, the first of these courses (Intro to Lasers) has been removed from the CORD Web site supposedly due to the expiration of their funding. Others may follow. While the courses are available for purchase in print form, It's a pity that this has happened. Print is not the same as on-line, even if it were free. I am looking into hosting them on one of my Web sites but suspect that in the end, such a request will be denied due to commercial interests winning out over availability of information.)

Here are the main table of contents (list of modules) for each course that presently exists or is under development:


Course 1: Intro to Lasers

1-1 Elements and Operation of a Laser
1-2 Elements and Operation of an Optical Power Meter
1-3 Introduction to Laser Safety
1-4 Properties of Light
1-5 Emission and Absorption of Light
1-6 Lasing Action
1-7 Optical Cavaties and Modes of Oscillation
1-8 Temporal Characteristics of Lasers
1-9 Spatial Characteristics of Lasers
1-10 Helium-Neon Gas Laser--A Case Study
1-11 Laser Classifications and Characteristics

Course 3: Laser Technology


3-1 Power Sources for CW Lasers
3-2 Pulsed Laser Flashlamps and Power Supplies
3-3 Energy Transfer in Solid-State Lasers
3-4 CW Nd:YAG Laser Systems
3-5 Pulsed Solid-State Laser Systems
3-6 Energy Transfer in Ion Lasers
3-7 Argon Ion Laser Systems
3-8 Energy Transfer in Molecular Lasers
3-9 CO2 Laser Systems
3-10 Liquid Dye Lasers
3-11 Semiconductor Lasers
3-12 Laser Q-Switching-Giant Pulses
3-13 Measurements of Laser Outputs
3-14 Laser Safety Hazards Evaluation

Course 4: Laser Electronics


4-1 Electrical Safety
4-2 Gas Laser Power Supplies
4-3 Ion Laser Power Supplies
4-4 Flashlamps for Pulsed Lasers and Flashlamps
4-5 Arc-Lamp Power Supplies
4-6 Diode Laser Power Supplies
4-7 Electro-Optic and Acousto-Optic Devices
4-8 Optical Detectors
4-9 Electro-Optic Instrumentation

Course 6: Laser and Electro-Optic Components


6-1 Optical Tables and Benches
6-2 Component Supports
6-3 Photographic Recording Mediums
6-4 Windows
6-5 Mirrors and Etalons
6-6 Filters and Beam Splitters
6-7 Prisms
6-8 Lenses
6-9 Gratings
6-10 Polarizers
6-11 Nonlinear Materials

Course 10: Laser and Electro-Optic Measurements


10-1 Spectrometers
10-2 Monochromators
10-3 Spectrophotometers
10-4 Michelson Interferometers
10-5 Fabry-Perot Interferometers
10-6 Twyan-Green Interferometers
10-7 Mach-Zehnder Interferometers
10-8 Spatial Resolution of Optical Systems

Applications of Photonics in Telecommunications (under construction)


Module 1: CW Nd: YAG Laser Systems
Module 2: Pulsed Solid-State Laser Systems
Module 3: Semiconductor Lasers
Module 4: Photodetector Characteristics
Module 5: Laser Information Systems
Module 6: Laser Distance Measurement
Module 7: Laser Trackers and Alignment Systems
Module 8: Laser/Fiber-Optic Communication Systems

The current Laser/Electro-Optics Technology (LEOT) curriculum materials are also available in print from CORD Communications.

This is all great educational content for those who wish to gain a better understanding of the principles of laser operation, find out what is in a laser, see examples of power supply circuits, and much more. But, it is designed at a level that shouldn't put you to sleep with too much heavy math. :-)

I would highly recommend that this site be bookmarked so you can refer to it for additional info on all sorts of laser related topics.


Another site which provides an outline of a course on lasers including summaries of laser types, applications, and laboratory experiments is: The Laser Adventure by Rami Arieli. I call it an outline because although most of the major topics are included, their coverage is quite brief and the serious student would need to find details elsewhere - perhaps from the CORD Communications Lasers and Electro-Optics courses described above. :-)
Some specific links with the most general interest are:


Table of Contents (Links to all chapters and sections of the course)
Laser Types (Summaries of major characteristics of most common lasers)
Laser Applications (Daily use, military, medical, scientific, industry, special)
Laboratory Experiments (Divergence, diffraction, measuring wavelength with a ruler, etc.)

Rockwell Laser International has a variety of short articles and summaries with info on laser theory, common laser types, wavelengths, and applications, a glossary, and more at their Laser Tutorials page.

MEOS GmbH is a developer of laser educational materials and equipment (among other things). Their Download Page has the lab/study manuals for their courses on a wide variety of laser related topics. While designed to be used in conjunction with the laboratory apparatus which they sell, these manuals include a great deal of useful information and procedures that can be applied in general.
The modules include (all in PDF format):


EXP01 Emission and Absorption
EXP03 Fabry Perot Resonator
EXP04 Diode Laser
EXP05 Second Harmonic Generation
EXP07 Generation of Short Pulses
EXP05 Nd:YAG Laser
EXP06 HeNe Laser
EXP09 CO2 Laser
EXP10 Michelson and Laser Interferometer
EXP11 Plastic Fibre Optics
EXP12 Glass Fibre Optics
EXP13 Optical Time Domain Reflectometry
EXP15 Laser Range Finder
EXP14 Erbium doped Fibre Amplifier
EXP19 Radio - and Photometry
EXP20 Laser safety
EXP27 Bar Code Reader


Also see the section: General Laser Information and Tutorial Sites for other sites that may be worth visiting.

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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, and carbon dioxide lasers.
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). Green and blue 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. Recent developments suggest that long lived room temperature blue and green diode lasers will be commercially available very soon. Violet (around 400 nm) laser diodes are just going into production.

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.

Power: .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.

Some applications: CD players and CDROM 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.

Cost: $15 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. Exteranl 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 single mode (TEM00).

Power: .5 to 10 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, LaserDisc and optical data storage.

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) 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: Violet-blue (457.9 nm), blue (488 nm - single line), green (514 nm), Red (Kr or Ar/Kr types only, 646 nm). Many other lines throughout the visible spectrum (and beyond) are available (but generally weaker) and may be 'dialed up' on some models.

Power: 10 mW to 10 W. Research lasers up to 100 W.

Beam quality: High to very high. Single 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; 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.

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.

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 could 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, high intensity discharge lamps, or high power laser diodes or arrays of laser diodes. 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.

Power: Varies widely. Peak in the TeraWatt range, 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.

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. :-)

The largest CW laser is probably a CO2 laser at the Troisk Institute for Thermonuclear Research(in Troisk, about 80 miles outside of Moscow, Russia). This is claimed to be 10 MegaWatt laser, 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.

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.