will reach its ground state or lowest state of energy. According to quantum mechanics there is only one light frequency that the atom will work with. There are three ways that the atom can deal with the presence of light either it can absorb the light, or spontaneous emission occurs, or stimulated emission occurs. This means that if the atom is at its lowest state that it may absorb the light and jump to its high state and emit extra light while doing so. The second thing it may do is if it is at its highest state it can fall spontaneously to its lower state thus emitting light. The third way is that the atom will jump from its upper state to its lower state thus emitting extra light. Spontaneous emission is not effected by light yet it is rather on a time scale characteristic of the states involved. That is called the spontaneous lifetime. In stimulated emission the frequency of the light is the same as the frequency of the light that stimulated it. Carbon-monoxide, color center, excimer, free-electron, gas-dynamic, helium-cadmium, hydrogen-fluoride, deuterium-fluoride, iodine, Raman spin-flip, and rare-gas halide lasers are just a few of the many types of lasers there are out there in the world. The helium-neon laser is the most common and by far the cheapest costing about $170. The diode laser is the smallest being packed in a transistor like package. The dye laser are very good for their broad, continuously variable wavelength capabilities. The theory of stimulated emission was first proved by Albert Einstein in 1916, then population inverse was discussed by V. A. Fabrikant in 1940. This led to the building of the first ammonia maser in 1954 by J. P. Gordon, H. J. Zeiger, and Charles H. Townes. In July of 1960 Theodore H. Maiman announced the generation of a pulse of coherent red light by means of a red crystal- the first laser. In 1987 Gordon Gould won a patent he had been trying to get for three years to build the first gas...
