Maser to Laser
A maser operates in a similar manner as the laser but produces and amplifies electromagnetic radiation mainly in the microwave region of the spectrum.
The invention of the maser (microwave amplification of stimulated emission of radiation) in 1954 by Charles Townes and Arthur Shawlow led to new investigations into light amplification by stimulated emissions of radiation, or laser, a term coined by American physicist Gordon Gould in 1957.
Gould, like Townes and his colleagues, had proposed using optical pumping to excite a maser, which originally used stimulated emission in a stream of energized ammonia molecules to produce amplification of microwaves. If the concept worked with visible light, the potential of the technology would be enormous, projecting the radio spectrum "into a range some ten thousand times higher than that which was previously attainable," Theodore Maiman said at a press conference held in New York City in July 1960. "Its success marks the opening of an entirely new era in electronics." (Read Maiman's remarks.)
At Hughes Research Laboratories, Maiman and his team had been investigating both the maser and laser concepts. Maiman proposed using ruby as the lasing medium, the substance that supplies the atoms or molecules to be stimulated. He set about demonstrating the laser concept in the spring of 1960.
How the Ruby Laser Works
A crystal of ruby was at the center of the first laser (a replica of which is shown above), providing the electrons to be stimulated. A fully reflecting mirror is placed on one end of the ruby cylinder and a partially reflecting mirror on the other. The cylinder is placed inside a high-intensity lamp, which provides a flash of white light that triggers the laser action. Wavelengths in the flash excite electrons to a higher energy level. Upon returning to their normal state, the electrons emit ruby-red light. The mirrors reflect some of the light back and forth inside the ruby crystal, stimulating other excited electrons to produce more red light, until the light pulse builds to high power, draining the energy stored in the ruby crystal.