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A maser (), an acronym for "microwave amplification by stimulated emission of radiation", is a device that produces coherent electromagnetic waves through amplification by stimulated emission. The first maser was built by Charles H. Townes, James P. Gordon, and H. J. Zeiger at Columbia University in 1953. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser. Masers are used as the timekeeping device in atomic clocks, and as extremely low-noise microwave amplifiers in radio telescopes and deep space spacecraft communication ground stations. Contemporary masers can be designed to generate electromagnetic waves at not only microwave frequencies but also radio and infrared frequencies. For this reason Charles Townes suggested replacing "microwave" with the word "molecular" as the first word in the acronym ''maser''.〔(Charles H. Townes – Nobel Lecture )〕 The laser works by the same principle as the maser, and the maser was the forerunner of the laser, inspiring theoretical work by Townes and Arthur Leonard Schawlow that led to its invention in 1960. When the coherent optical oscillator was first imagined in 1957, it was originally called the "optical maser." This was ultimately changed to laser for "Light Amplification by Stimulated Emission of Radiation." Gordon Gould is credited with creating this acronym in 1957. ==History== The theoretical principles describing the operation of a maser were first described by Nikolay Basov and Alexander Prokhorov from Lebedev Institute of Physics at an ''All-Union Conference on Radio-Spectroscopy'' held by the USSR Academy of Sciences in May 1952. The results were subsequently published in October 1954. A precursor of the maser was a hydrogen device built and tested by the physicists Theodor V. Ionescu and Vasile Mihu in 1946. Independently, Charles H. Townes, James P. Gordon, and H. J. Zeiger built the first ammonia maser at Columbia University in 1953. This device used stimulated emission in a stream of energized ammonia molecules to produce amplification of microwaves at a frequency of about 24.0 gigahertz. Townes later worked with Arthur L. Schawlow to describe the principle of the ''optical maser'', or ''laser'', of which Theodore H. Maiman created the first working model in 1960. For their research in the field of stimulated emission, Townes, Basov and Prokhorov were awarded the Nobel Prize in Physics in 1964. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Maser」の詳細全文を読む スポンサード リンク
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