In 1916, Albert Einstein developed the theory of Stimulated Emission.  Simply put, it is a process where a photon is emitted from an atom and crashed into other atoms, causing them to also emit photons.  In a vacuum chamber, more and more photons bounce around, raising the energy level within the chamber.  When the energy has built up sufficiently, it exits the chamber as a narrow beam of light.  Although Einstein’s work was explored during the 1920s, it was largely forgotten until, in 1954, Charles Townes, an American physicist, started investigating microwave light. 

The 60s heralded new breakthroughs in laser technology.  Theodore Maiman built the first working optical light laser in 1960.  It used a solid state laser that incorporated a synthetic ruby.  Working separately from Maiman, Ali Javan, William Bennet and Donald Herriot made the first gas laser using helium and neon in the same year.  The first semiconductor laser was developed in 1962.

Today, the three most common lasers are gas, solid state and semiconductor. 

Helium-neon lasers

Helium-neon lasers are the cheapest visible light lasers.  In 1974, they were used as bar code scanners, first in grocery stores and now in many large retail stores.  The laser is scanned across a bar code and tells the cash register’s computer the price of the item.  It can also provide information on sale discounts, stock numbers and inventory.

Lasers are used by surveyors and machinists to measure distance and align parts.  They are used to measure the speed of light in a laboratory, distances on a street or movement along an earthquake fault.  Nearly all major sewer pipe and storm drain pipe installations are aligned using helium-neon lasers.  

Argon lasers

Argon lasers are used by the medical profession to make incisions that are more precise than scalpels.  There is less scarring with lasers because they can be used in place of sutures to fuse the incision together after surgery.  Lasers are used in eye surgery to weld the retina back together. Lasers are also used to correct poor vision by reshaping the cornea.  One of the newest medical uses for lasers is to make small holes in the heart so that pathways are created for new blood flow. This helps prevent heart attacks.  The only downside is the increased cost over traditional surgeries. 

Argon lasers make holograms, and are used in spectrochemistry, optical image processing, semiconductor processing and laser light shows.  In the 70s, krypton lasers were used for the red beams and argon lasers for the blue and green beams. 

Solid state lasers

Solid state lasers are used for cutting, welding, heat treating and marking of materials.  Jewelers can very precise cuts when using lasers to cut fine gems.  Lasers allow better cuts on metals and the welding of dissimilar metals. 

Scientists use solid state lasers to detect the slightest movements in matter.  Law enforcement has long used laser technology for gauging the speed of cars.  The military is using solid state lasers in rangefinders, laser guided bombs and satellite communications systems.  Under investigation is the advanced tactical laser similar to the ray guns of Buck Rogers, Flash Gordon, and Hans Solo.

The largest lasers in the world are solid state lasers. Many of the laser projectors for light shows and for other laser displays use solid state rather than argon or krypton gas lasers.

Semiconductor lasers

Semiconductors are used to produce lasers with invisible light.  The first successful consumer product to include a laser, the laserdisc player, was introduced in 1978.  Light was reflected from a disc to a detector.  The pattern of holes in the disc was then converted to a digital signal that contained the coded audio information.  In 1983, the compact disc player was introduced.  Working on the same principle as the laserdisc player, it became the first laser-equipped device to be found in a majority of American homes.  Currently, lasers are also used in DVD players, cellular phones, laser printers  and wireless Internet transmission.