Laser

In the 1950s, there was a push by scientists to develop sources of coherent electromagnetic radiation at wavelengths shorter than vacuum tubes could provide. Charles Townes and co-workers at Columbia University, New York, developed the ammonia maser (microwave amplification by stimulated emission of radiation) in 1954, a device which produced coherent microwaves. In 1958, Townes and Art Schawlow published the principles of a maser operating in the visible region of the electromagnetic spectrum. The first successful demonstration of a laser followed in 1960 by Theodore Maiman of Hughes Laboratories, who operated a pulsed ruby laser which generated several kilowatts of optical power.

In the following few years, several different laser systems were demonstrated in gases (helium neon mixture, carbon dioxide, argon, krypton) and solids (uranium, samarium, neodymium, nickel, cobalt, and vanadium ions implanted in electrically insulating crystalline hosts). Since that time, laser action has been demonstrated in many different materials, involving all four states of matter (solid, liquid, gas, and plasma), covering the range of wavelengths from x rays to submillimeter waves. Only a few types of laser find widespread use because of issues such as efficiency, ease of use, reliability, and cost.