Masers were also used as low-noise microwave amplifiers in radio telescopes, though these have largely been replaced by amplifiers based on FETs. These "atomic frequency standards" are one of the many forms of atomic clocks. Masers serve as high precision frequency references. In 2018, a research team from Imperial College London and University College London demonstrated continuous-wave maser oscillation using synthetic diamonds containing nitrogen-vacancy defects. It produced pulses of maser emission lasting for a few hundred microseconds. In 2012, a research team from the National Physical Laboratory and Imperial College London developed a solid-state maser that operated at room temperature by using optically pumped, pentacene-doped p-Terphenyl as the amplifier medium. Dual noble gas maser (The dual noble gas of a masing medium which is nonpolar.Whispering-gallery modes iron-sapphire maser.When atoms have been induced into an excited energy state, they can amplify radiation at a frequency particular to the element or molecule used as the masing medium (similar to what occurs in the lasing medium in a laser).īy putting such an amplifying medium in a resonant cavity, feedback is created that can produce coherent radiation. The maser is based on the principle of stimulated emission proposed by Albert Einstein in 1917. Maiman created the first working model in 1960.įor their research in the field of stimulated emission, Townes, Basov and Prokhorov were awarded the Nobel Prize in Physics in 1964. Schawlow to describe the principle of the optical maser, or laser, of which Theodore H. 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. Zeiger built the first ammonia maser at Columbia University in 1953. Independently, Charles Hard Townes, James P. The theoretical principles governing the operation of a maser were first described by Joseph Weber of the University of Maryland, College Park at the Electron Tube Research Conference in June 1952 in Ottawa, with a summary published in the June 1953 Transactions of the Institute of Radio Engineers Professional Group on Electron Devices, and simultaneously 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, subsequently published in October 1954. Gordon Gould is credited with creating this acronym in 1957. This was ultimately changed to laser for "Light Amplification by Stimulated Emission of Radiation". When the coherent optical oscillator was first imagined in 1957, it was originally called the "optical maser". The maser was the forerunner of the laser, inspiring theoretical work by Townes and Arthur Leonard Schawlow that led to the invention of the laser in 1960 by Theodore Maiman. The laser works by the same principle as the maser but produces higher frequency coherent radiation at visible wavelengths. For this reason, Townes suggested replacing microwave with the word molecular as the first word in the acronym maser. Modern masers can be designed to generate electromagnetic waves at not only microwave frequencies but also radio and infrared frequencies. Masers are also 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. Townes, Nikolay Basov and Alexander Prokhorov were awarded the 1964 Nobel Prize in Physics for theoretical work leading to the maser. A hydrogen radio frequency discharge, the first element inside a hydrogen maser (see description below)Ī maser ( / ˈ m eɪ z ər/, an acronym for microwave amplification by stimulated emission of radiation) is a device that produces coherent electromagnetic waves through amplification by stimulated emission.
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