The name LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation. It is is a device that emits a beam of light through a process called optical amplification. It distinguishes itself from other sources of light by emitting light in a spatially and temporally coherent manner. Spatial coherence keeps the beam within a narrow and tight path over long disances. This allows the energy generated to be used in applications such as laser cutting and laser pointing. Having temporal coherence means that can emit light within a narrow spectrum to generate a light beam of a specific color.
In 1917, Albert Einstein first theorized about the process which makes lasers possible called "Stimulated Emission." He detailed his theory in a paper titled Zur Quantentheorie der Strahlung (On the Quantum Theory of Radiation). Today, lasers are used in a wide range of technologies including optical disk drives, laser printers and barcode scanners. They are also used in laser surgery and skin treatments as well as cutting and welding.
Before the Laser
In 1954, Charles Townes and Arthur Schawlow invented the maser (microwave amplification by stimulated emission of radiation) using ammonia gas and microwave radiation. The maser was invented before the (optical) laser. The technology is very similar but does not use visible light.
On March 24, 1959, Townes and Schawlow were granted a patent for the maser. The maser was used to amplify radio signals and as an ultra sensitive detector for space research.
In 1958, Townes and Schawlow theorized and published papers about a visible laser, an invention that would use infrared and/or visible spectrum light. However, they did not proceed with any research at the time.
Many different materials can be used as lasers. Some, like the ruby laser, emit short pulses of laser light. Others, like helium-neon gas lasers or liquid dye lasers, emit a continuous beam of light.
The Ruby Laser
In 1960, Theodore Maiman invented the ruby laser considered to be the first successful optical or light laser.
Many historians claim that Maiman invented the first optical laser. However, there is some controversy due to claims that Gordon Gould was the first and there is good evidence backing that claim.
The Gordon Gould Laser
Gould was the first person to use the word "laser." Gould was a doctoral student at Columbia University under Townes, the inventor of the maser. Gould was inspired to build his optical laser starting in 1958. He failed to file for a patent his invention until 1959. As a result, Gould's patent was refused and his technology was exploited by others. It took until 1977 for Gould to finally win his patent war and receive his first patent for the laser.
The Gas Laser
The first gas laser (helium-neon) was invented by Ali Javan in 1960. The gas laser was the first continuous-light laser and the first to operate "on the principle of converting electrical energy to a laser light output." It has been used in many practical applications.
Hall's Semiconductor Injection Laser
In 1962, inventor Robert Hall created a revolutionary type of laser that is still used in many of the electronic appliances and communications systems that we use every day.
Patel's Carbon Dioxide Laser
The carbon dioxide laser was invented by Kumar Patel in 1964.
Walker's Laser Telemetry
Hildreth Walker invented laser telemetry and targeting systems.
Laser Eye Surgery
New York City ophthalmologist Steven Trokel made the connection to the cornea and performed the first laser surgery on a patient's eyes in 1987. The next ten years were spent perfecting the equipment and the techniques used in laser eye surgery. In 1996, the first Excimer laser for ophthalmic refractive use was approved in the United States.
Trokel patented the Excimer laser for vision correction. The Excimer laser was originally used for etching silicone computer chips in the 1970s. Working in the IBM research laboratories in 1982, Rangaswamy Srinivasin, James Wynne and Samuel Blum saw the potential of the Excimer laser in interacting with biological tissue. Srinivasin and the IBM team realized that you could remove tissue with a laser without causing any heat damage to the neighboring material.
But it took the observations of Dr. Fyodorov in a case of eye trauma in the 1970's to bring about the practical application of refractive surgery through radial keratotomy.