Maser

A maser is any amplifier that produces coherent electromagnetic waves due to stimulated emission.

Uses

Masers serve as high precision frequency references, as, for example in an atomic clock. They are also used as electronic amplifiers in radio telescopes. For more information about frequency reference masers, see atomic clock.

Related Topics:
Frequency - Atomic clock - Electronic amplifier - Radio telescopes

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Another example is given by telescopic masers, which may use arrays of chromium atoms in an insulating aluminium oxide crystal as amplifiers, pumping the energy in at a different radio frequency. That is, they use polished strips of synthetic ruby. As the input signal comes in, a gold comb (made of gold because it is slow to corrode and change shape) distributes the signal along the strip of polished ruby. As the radio wave moves through the crystal, it knocks electrons into different atomic orbitals. As the electrons move to their new lower energy orbits, they add to the wave that knocked them down, leading to a population inversion. The comb-fingers are spaced so that the desired radio waves add together as they move down the crystal. This means that unwanted radio waves will not add together, and are therefore filtered out, leading to a highly coherent induced emission.

Related Topics:
Arrays - Chromium - Atoms - Aluminium oxide - Crystal - Energy - Synthetic - Ruby - Gold - Electrons - Atomic orbitals - Energy orbits - Wave - Population inversion - Filtered - Coherent - Emission

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An example of a maser which operates in the radio frequency range of the spectrum, is the spin-exchange Zeeman maser. Here, coupled spins from different atoms can exchange (ie. sometimes from the electronic to the nuclear) in order to generate a coherency in the system that radiates in, for example, the VLF region of the electromagnetic spectrum. These types of masers are sometimes called rf-lasers or rasers for short (though most often simply called masers).

Related Topics:
Spin-exchange - Zeeman - VLF - Electromagnetic spectrum - Rf

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See http://arxiv.org/find/grp_physics/1/ti:+maser/0/1/0/all/0/1?per_page=100 for an expansive list of articles on masers.

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Masers are also currently being studied by the United States Military as a form of vehicle-mounted riot control device. A maser can be used to heat up water molecules in the skin, producing a burning sensation without causing permanent damage, unless concentrated on a target for an extended period of time.

Related Topics:
United States Military - Riot control - Water molecule - Skin - Burning - Permanent

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