Rubin Braunstein (1922–2018) was an American physicist and educator. In 1955 he published the first measurements of light emission by semiconductor diodes made from crystals of gallium arsenide (GaAs), gallium antimonide (GaSb), and indium phosphide (InP). GaAs, GaSb, and InP are examples of

III-V semiconductors Semiconductor materials are nominally small band gap insulators. The defining property of a semiconductor material is that it can be compromised by doping it with impurities that alter its electronic properties in a controllable way. Because of t ...

. The III-V semiconductors absorb and emit light much more strongly than silicon, which is the best-known semiconductor. Braunstein's devices are the forerunners of contemporary

LED lighting An LED lamp or LED light bulb is an electric light that produces light using light-emitting diodes (LEDs). LED lamps are significantly more energy-efficient than equivalent incandescent lamps and can be significantly more efficient than mos ...

and semiconductor lasers, which typically employ III-V semiconductors. The 2000 and 2014 Nobel Prizes in Physics were awarded for further advances in closely related fields. Braunstein was raised in New York City. He earned a doctorate in physics from

Syracuse University Syracuse University (informally 'Cuse or SU) is a Private university, private research university in Syracuse, New York. Established in 1870 with roots in the Methodist Episcopal Church, the university has been nonsectarian since 1920. Locate ...

in 1954. He then joined the research laboratory of the

RCA Corporation The RCA Corporation was a major American electronics company, which was founded as the Radio Corporation of America in 1919. It was initially a patent trust owned by General Electric (GE), Westinghouse, AT&T Corporation and United Fruit Comp ...

, which was among the most active industrial laboratories at the time. In the following decade at RCA Laboratories he published broadly on semiconductor physics and technology. Beyond his seminal work with light emission from III-V semiconductors, in 1964 he exploited newly invented lasers to publish the first paper on

two-photon absorption Two-photon absorption (TPA or 2PA) or two-photon excitation or non-linear absorption is the simultaneous absorption of two photons of identical or different frequencies in order to excite a molecule from one state (usually the ground state) to a hi ...

in semiconductors. Typically, only individual

photons A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they alway ...

(particles of light) with some minimum energy are absorbed by a given semiconductor. For very high intensity beams of light, two photons, each with half that minimum energy, can be absorbed simultaneously. He also published highly cited foundation papers on the electronic, optical, and vibrational properties of III-V semiconductors, silicon, and germanium. In 1964 Braunstein became a professor of physics at

University of California, Los Angeles The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...

(UCLA), where he remained for the rest of his career. His research there continued his RCA work with optoelectronic properties of semiconductors as well as contributions related to the optical properties of highly transparent materials such as tungstate glasses. Some of Braunstein's work was theoretical, including the proposal that neutral atoms could be scattered by a sufficiently intense

standing wave In physics, a standing wave, also known as a stationary wave, is a wave that oscillates in time but whose peak amplitude profile does not move in space. The peak amplitude of the wave oscillations at any point in space is constant with respect ...

of light. Since light is an electromagnetic wave, it had long been known that charged particles like electrons would be scattered. The effect with neutral atoms is much weaker, but was finally observed nearly 20 years after the proposal of Braunstein and his co-authors. Braunstein was selected as a Fellow of the

American Physical Society The American Physical Society (APS) is a not-for-profit membership organization of professionals in physics and related disciplines, comprising nearly fifty divisions, sections, and other units. Its mission is the advancement and diffusion of k ...

in 1964.

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