In 1917, A. Einstein stated the principle of stimulated emission, which paved the way to the new technology: LASER "Light Amplification by Stimulated Emission of Radiation". But it was not until 1960 that Theodor Maiman designed the first solid-state laser. In1961, A.Javan put into operation the first gas laser, forerunner of industrial lasers in today's industry.
The laser effect relies on coherent light amplification by stimulated emission. Most optical amplifiers are based on the laser effect. A laser source is the source of spatially and temporally coherent light based on the laser effect. Originally, the acronym LASER derived from maser.
A laser source combines an optical amplifier based on the optical-cavity laser effect also known as resonator consisting typically of two mirrors, one of which is partially reflective, i.e. a quantity of light comes out of the cavity, while the rest of light is reinjected into the laser cavity.
The geometrical properties of this set-up require
- the emitted beam be basically less divergent, i.e. spatially coherent. With some long cavities, the laser light can be highly directional
- the radiation emitted is a high spectral purity, i.e. temporally coherent
The radiation spectrum contains a discrete set of thin rays at wavelengths defined by the cavity and laser medium. The thinness of these rays is limited by the cavity stability and spontaneous emission within the amplifier (quantum noise). Different techniques enable emission around a single wavelength.
Microwaves (maser), then infrared, visible light, ultraviolet and even X-rays have been the initial related wavelengths.
Courtesy of IREPA LASER
