Maser in the context of "Stimulated emission"

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๐Ÿ‘‰ Maser in the context of Stimulated emission

Stimulated emission is the process by which an incoming photon of a specific frequency can interact with an excited atomic electron (or other excited molecular state), causing it to drop to a lower energy level. The liberated energy transfers to the electromagnetic field, creating a new photon with a frequency, polarization, and direction of travel that are all identical to the photons of the incident wave. This is in contrast to spontaneous emission, which occurs at a characteristic rate for each of the atoms/oscillators in the upper energy state regardless of the external electromagnetic field.

According to the American Physical Society, the first person to correctly predict the phenomenon of stimulated emission was Albert Einstein in a series of papers starting in 1916, culminating in what is now called the Einstein B Coefficient. Einstein's work became the theoretical foundation of the maser and the laser. The process is identical in form to atomic absorption in which the energy of an absorbed photon causes an identical but opposite atomic transition: from the lower level to a higher energy level. In normal media at thermal equilibrium, absorption exceeds stimulated emission because there are more electrons in the lower energy states than in the higher energy states. However, when a population inversion is present, the rate of stimulated emission exceeds that of absorption, and a net optical amplification can be achieved. Such a gain medium, along with an optical resonator, is at the heart of a laser or maser.Lacking a feedback mechanism, laser amplifiers and superluminescent sources also function on the basis of stimulated emission.

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Maser in the context of Atomic, molecular, and optical physics

Atomic, molecular, and optical physics (AMO) is the study of matterโ€“matter and lightโ€“matter interactions, at the scale of one or a few atoms and energy scales around several electron volts. The three areas are closely interrelated. AMO theory includes classical, semi-classical and quantum treatments. Typically, the theory and applications of emission, absorption, scattering of electromagnetic radiation (light) from excited atoms and molecules, analysis of spectroscopy, generation of lasers and masers, and the optical properties of matter in general, fall into these categories.

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Maser in the context of Charles H. Townes

Charles Hard Townes (July 28, 1915 โ€“ January 27, 2015) was an American physicist. Townes worked on the theory and application of the maser, for which he obtained the fundamental patent, and other work in quantum electronics associated with both maser and laser devices. He shared the 1964 Nobel Prize in Physics with Nikolay Basov and Alexander Prokhorov. Townes was an adviser to the United States Government, meeting every US president from Harry S. Truman (1945) to Bill Clinton (1999).

He directed the US government's Science and Technology Advisory Committee for the Apollo lunar landing program. After becoming a professor of the University of California, Berkeley in 1967, he began an astrophysical program that produced several important discoveries, for example, the black hole at the center of the Milky Way galaxy.

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Maser in the context of Arthur Leonard Schawlow

Arthur Leonard Schawlow (May 5, 1921 โ€“ April 28, 1999) was an American physicist who, along with Charles Townes, developed the theoretical basis for laser science. His central insight was the use of two mirrors as the resonant cavity to take maser action from microwaves to visible wavelengths. He shared the 1981 Nobel Prize in Physics with Nicolaas Bloembergen and Kai Siegbahn for his work using lasers to determine atomic energy levels with great precision.

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