In 1917, Einstein laid the foundation for the laser when he introduced the concept of stimulated emission; where a photon interacts with an excited molecule or atom and causes the emission of a second photon having the same frequency, phase, polarization and direction. The acronym LASER stands for "Light Amplification by Stimulated Emission of Radiation".
The First Laser
Theodore Maiman developed the first working laser at Hughes Research Lab in 1960, and his paper describing the operation of the first laser was published in Nature three months later. Since then, more than 55,000 patents involving the laser have been granted in the United States. Today's laser and all of its applications are the result of not one individual's efforts, but the work of a number of prestigious scientists and engineers who were leaders in optics and photonics over the course of history. These include such great minds as Charles Townes at Columbia University, who developed the maser, the precursor to the laser, and Arthur Schawlow at Bell Laboratories, who along with Townes published a key theoretical paper in 1958 that helped lead to the lasers development and who jointly were awarded the first laser patent in 1960.
Maiman's early laser used a powerful energy source to excite atoms in a synthetic ruby to higher energy levels. At a specific energy level, some atoms emitted particles of light called photons. These newly created photons struck other atoms, rapidly stimulating the emission of more identical photons and amplifying the light intensity. Maiman was able to continue this process of stimulated emission and amplification by placing a completely reflecting silver mirror on one end of the model and a partially reflecting silver mirror on the other. This setup enabled photons to bounce back and forth between the mirrors until they gained enough intensity to burst through the partially silvered end as a powerful, coherent, beam of light--what you can today find on the end of a laser pointer.
A predecessor of the laser, called the MASER, for "Microwave Amplification by Stimulated Emission of Radiation", was independently developed in 1954 at Columbia University by Charles Townes and Jim Gordon and in Russia by Nicolay Basov and Alexsandr Prokhorov. These ammonia masers were two-energy-level gaseous systems that could continuously sustain a population inversion and oscillation. In 1956 Nicolaas Bloembergen proposed a three-level solid state maser at Harvard, demonstrated by researchers at Bell Labs that same year.
Soon after the maser, Arthur Schawlow and Charles Townes began thinking about ways to make infrared or visible light masers. In 1957 Schawlow and Townes constructed an optical cavity by placing two highly reflecting mirrors parallel to each other, and positioning the amplifying medium in between. In 1958, they published a seminal Physical Review paper on their findings and submitted a patent application for the so-called optical maser.
The lengthy Physical Review article was widely read in the United States, and generated considerable interest among other researchers, especially experimentalists who attempted to build the first laser. Although the paper rightfully gave Schawlow and Townes recognition as having invented the laser, several others independently came up with the same "open cavity" concept, including Gordon Gould, a graduate student at Columbia University. Gould was also the first to publically use the term laser, for "Light Amplification by Stimulated Emission of Radiation" at the June 1959 Ann Arbor Optical Pumping Conference.
Laser Patent War
Gould filed a laser patent in April 1959 but this was denied by the US Patent Office in favor of the Schawlow and Townes optical maser patent (awarded 1960). This led to what is often called the "Thirty Year Patent War", with Gould eventually winning 48 patents many years later for commercially valuable aspects of lasers including optical pumping and specific applications.
More Laser History
The first laser
Charles H. Townes
from A Century of Nature: Twenty-One Discoveries that Changed Science and the World Laura Garwin and Tim Lincoln, editors
Race to Build the Laser
After the Schawlow-Townes Physical Review paper was published in 1958, a furious competition ensued to build the first working laser involving institutions such as Bell Labs, Hughes Research Labs, RCA Labs, Lincoln Labs, IBM, Westinghouse, and Siemens. Theodore Maiman at Hughes Research Labs realized that high gain pulsed oscillation could be achieved in ruby by optically pumping with commercial flash lamps, and in May 1960 demonstrated the first working laser. This laser was so easy to build that within weeks several other groups duplicated the achievement.
In 1964, Townes shared the Nobel Prize in Physics with Prokhorov and Basov of the Lebedev Institute in Moscow, for "fundamental work in the field of quantum electronics which has led to the construction of oscillators and amplifiers based on the maser-laser principle."
The first widely recognized application of the laser appeared in 1974, with the introduction of bar code scanners, following the invention of the laser printer three years earlier, in 1971.
Arthur Schawlow and Nicolaas Bloembergen are jointly awarded one half of the Nobel Prize in Physics for their "contribution to the development of laser spectroscopy." The other half is awarded to Kai M. Siegbahn "for his contribution to the development of high-resolution electron spectroscopy.