1916 Albert Einstein postulates that if an atom is in an excited state and receives a photon, it will stimulate the atom to emit a photon of the same energy and drop to a lower level. This process is known as stimulated emission.

1954 With the development of radar in World War II, interest in the microwave part of the spectrum increased. After coming up with the idea while sitting on a park bench, Charles H. Townes builds the world's first MASER, an acronym for microwave amplification by stimulated emission of radiation. Here Townes (left), and an associate James P. Gordon display their second-generation MASER.

1960 Theodore H. Maiman creates the first laser at Hughes Research Laboratories using a synthetic ruby and aluminum oxide doped with chromium atoms. Hughes management was skeptical of his work: by the time Maiman got the laser to fire, he had been assigned to another project.

1961 Basov proposes using p-n junctions in a semiconductor to produce stimulated emission. He devotes time to theoretical research in the field.

1962 Robert Hall, working for General Electric's Research and Development Laboratories in Schenectady, NY, creates the first diode laser. Using p-n junctions in gallium arsenide, cooled to 77K (the boiling point of nitrogen), Hall's laser output a light with a wavelength of 840 nm. Unfortunately, this laser required a current density of 10,000 amps per square centimeter, and generated so much heat that it could only operate in a pulsed mode at 77K.

1968 The double heterojunction or double heterostructure laser, where the active layer is sandwiched between two layers of a slightly different material, is first built. In this configuration, both light and current are trapped in the active layer by using a material with a band gap energy larger than in the active layer. This allows the diode laser to function at room temperatures.

1970 Groups at both Bell Labs and the Soviet Union make the first semiconductor lasers that could operate continuously at room temperature. However, it lasted only a few hours before failing. Here Izou Hayashi is shown holding the Bell Labs diode laser.

1972 Mass production of LEDs begins.

1982 The laser diode used in CD players is created. This device outputs 5mW infrared light at a wavelength of 780nm.

1995 Digital Versatile Disks (DVDs) first enter the market. DVD players use a diode laser which emits light at 635nm. This use of a a shorter wavelength allows media with smaller pits to be read, thus enabling a disc the size of a CD to hold approximately eight times as much data.