Lichtquant

Lichtquant, literally "quantum of light," denotes the quantum of the electromagnetic field and is commonly identified with the photon in modern physics. It is the fundamental unit of light in quantum theory, enabling the discrete exchange of energy between light and matter. A Lichtquant has zero rest mass, travels at the speed of light in vacuum, carries energy E = hν and momentum p = h/λ, and possesses spin angular momentum of 1 (in units of ħ). Its properties reflect both particle-like and wave-like behavior, a cornerstone of modern quantum electrodynamics.

Historical background and terminology: The concept arose from Planck’s explanation of blackbody radiation and was extended by Albert Einstein in 1905 to account for the photoelectric effect. In German-language literature, the term Lichtquant is used, while in English the standard term is photon.

Interactions and generation: Lichtquanten are created or annihilated in atomic or molecular transitions, spontaneous and stimulated emission, and various radiation processes. They interact with matter through quantized energy exchange and can exhibit interference and diffraction as waves when not measured as particles. Detection methods include photodetectors, photomultipliers, and single-photon detectors, which resolve frequency, polarization, and arrival time.

Importance and applications: The Konzept of the Lichtquant is central to quantum optics, photonics, and quantum information science. Practical applications span lasers, photovoltaic devices, optical communications, spectroscopy, and emerging quantum technologies.

See also: Photon, Planck constant, Einstein, photoelectric effect.