Lasers (standing for Light Amplification by Stimulated Emission of Radiation) are now part of everyday life. They form a key component of CD and DVD players and the scanners used at supermarket checkouts. Their ability to direct energy with pinpoint precision give them a wide spectrum of uses as dental drills,metal cutters, welders, and scalpels for eye surgery.
The laser process- begins with a population of atoms that has, been optically pumped so that there are more atoms at a higher energy level than at a lower level. Decay then produces photons of light that stimulate the emission of other decays and so a cascade of photons is produced. The lasing substance is contained in a resonant cavity that has mirrors at each end. Photons travel back and forth between the two mirrors stimulating feedback and the system "lases" if the gain due to stimulated emission exceeds the losses due to absorption and scattering. One of the mirrors is half silvered and the radiation that passes through this forms the beam of laser light.
Albert Einstein discussed stimulated emission as early as 1916, but the actual phenomenon was first produced in 1954 using microwaves (therefore MASER). In May 1960 Theodore Maiman (1927-2007) who was working at the Hughes Research laboratories in California, used a synthetic ruby crystal to produce the first operating pulsed laser.
There are now many different kinds of lasing materials. Some are solid, such as ruby and garnet, whereas others are gases such as helium and liquid solutions of organic dyes.
