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Photon Noise
Photon noise is the randomness in signal associated with photons arriving at a detector. For a simple black body emitting on an absorber, the noise-equivalent power is given by :\mathrm^2 = 2 h^2 \nu^2 \Delta\nu \left( \frac + n^2 \right) where h is the Planck constant, \nu is the central frequency, \Delta\nu is the bandwidth, n is the occupation number and \eta is the optical efficiency. The first term is essentially shot noise whereas the second term is related to the bosonic character of photons, variously known as "Bose noise" or "wave noise". At low occupation number, such as in the visible spectrum, the shot noise term dominates. At high occupation number, however, typical of the radio spectrum, the Bose term dominates. See also * Hanbury Brown and Twiss effect In physics, the Hanbury Brown and Twiss (HBT) effect is any of a variety of correlation and anti-correlation effects in the intensity (physics), intensities received by two detectors from a beam of particles. H ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photon
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 particles that can move no faster than the speed of light measured in vacuum. The photon belongs to the class of boson particles. As with other elementary particles, photons are best explained by quantum mechanics and exhibit wave–particle duality, their behavior featuring properties of both waves and particles. The modern photon concept originated during the first two decades of the 20th century with the work of Albert Einstein, who built upon the research of Max Planck. While Planck was trying to explain how matter and electromagnetic radiation could be in thermal equilibrium with one another, he proposed that the energy stored within a material object should be regarded as composed of an integer number of discrete, equal-sized parts. To explain the pho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Body
A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. The radiation emitted by a black body in thermal equilibrium with its environment is called ''black-body radiation''. The name "black body" is given because it absorbs all colors of light. In contrast, a white body is one with a "rough surface that reflects all incident rays completely and uniformly in all directions." A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition. An ideal black body in thermal equilibrium has two main properties: #It is an ideal emitter: at every frequency, it emits as much or more thermal radiative energy as any other body at the same temperature. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Noise-equivalent Power
Noise-equivalent power (NEP) is a measure of the sensitivity of a photodetector or detector system. It is defined as the signal power that gives a signal-to-noise ratio of one in a one hertz output bandwidth. An output bandwidth of one hertz is equivalent to half a second of integration time.The factor of one half is explained by the Nyquist–Shannon sampling theorem. The units of NEP are watts per square root hertz. The NEP is equal to the noise amplitude spectral density (expressed in units of \mathrm/\sqrt or \mathrm/\sqrt) divided by the responsivity Responsivity is a measure of the input–output Gain (electronics), gain of a detector system. In the specific case of a photodetector, it measures the electrical output per optical input. A photodetector's responsivity is usually expressed in un ... (expressed in units of \mathrm/\mathrm or \mathrm/\mathrm, respectively). The fundamental equation is SNR = P/NEP. A smaller NEP corresponds to a more sensitive detector. For exa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Planck Constant
The Planck constant, or Planck's constant, denoted by h, is a fundamental physical constant of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a matter wave equals the Planck constant divided by the associated particle momentum. The constant was postulated by Max Planck in 1900 as a proportionality constant needed to explain experimental black-body radiation. Planck later referred to the constant as the "quantum of Action (physics), action". In 1905, Albert Einstein associated the "quantum" or minimal element of the energy to the electromagnetic wave itself. Max Planck received the 1918 Nobel Prize in Physics "in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta". In metrology, the Planck constant is used, together with other constants, to define the kilogram, the SI unit of mass. The SI units are defined in such a way that, w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Occupation Number
In quantum mechanics, a Fock state or number state is a quantum state that is an element of a Fock space with a well-defined number of particles (or quanta). These states are named after the Soviet physicist Vladimir Fock. Fock states play an important role in the second quantization formulation of quantum mechanics. The particle representation was first treated in detail by Paul Dirac for bosons and by Pascual Jordan and Eugene Wigner for fermions. The Fock states of bosons and fermions obey useful relations with respect to the Fock space creation and annihilation operators. Definition One specifies a multiparticle state of ''N'' non-interacting identical particles by writing the state as a sum of tensor products of ''N'' one-particle states. Additionally, depending on the integrality of the particles' spin, the tensor products must be alternating (anti-symmetric) or symmetric products of the underlying one-particle Hilbert spaces. Specifically: * Fermions, having half-inte ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shot Noise
Shot noise or Poisson noise is a type of noise which can be modeled by a Poisson process. In electronics shot noise originates from the discrete nature of electric charge. Shot noise also occurs in photon counting in optical devices, where shot noise is associated with the particle nature of light. Origin In a statistical experiment such as tossing a fair coin and counting the occurrences of heads and tails, the numbers of heads and tails after many throws will differ by only a tiny percentage, while after only a few throws outcomes with a significant excess of heads over tails or vice versa are common; if an experiment with a few throws is repeated over and over, the outcomes will fluctuate a lot. From the law of large numbers, one can show that the relative fluctuations reduce as the reciprocal square root of the number of throws, a result valid for all statistical fluctuations, including shot noise. Shot noise exists because phenomena such as light and electric curren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Boson
In particle physics, a boson ( ) is a subatomic particle whose spin quantum number has an integer value (0, 1, 2, ...). Bosons form one of the two fundamental classes of subatomic particle, the other being fermions, which have half odd-integer spin (1/2, 3/2, 5/2, ...). Every observed subatomic particle is either a boson or a fermion. Paul Dirac coined the name ''boson'' to commemorate the contribution of Satyendra Nath Bose, an Indian physicist. Some bosons are elementary particles occupying a special role in particle physics, distinct from the role of fermions (which are sometimes described as the constituents of "ordinary matter"). Certain elementary bosons (e.g. gluons) act as force carriers, which give rise to forces between other particles, while one (the Higgs boson) contributes to the phenomenon of mass. Other bosons, such as mesons, are composite particles made up of smaller constituents. Outside the realm of particle physics, multiple identical composite bosons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Satyendra Nath Bose
Satyendra Nath Bose (; 1 January 1894 – 4 February 1974) was an Indian theoretical physicist and mathematician. He is best known for his work on quantum mechanics in the early 1920s, in developing the foundation for Bose–Einstein statistics, and the theory of the Bose–Einstein condensate. A Royal Society#Fellows, Fellow of the Royal Society, he was awarded India's second highest civilian award, the Padma Vibhushan, in 1954 by the Government of India. The class of particles that obey Bose statistics, bosons, was named after Bose by Paul Dirac. A polymath, he had a wide range of interests in varied fields, including physics, mathematics, chemistry, biology, mineralogy, philosophy, The arts, arts, literature, and music. He served on many research and development committees in India, after independence. Early life Bose was born in Calcutta (now Kolkata), the eldest of seven children in a Bengali Kayastha family. He was the only son, with six sisters after him. His ance ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visible Spectrum
The visible spectrum is the spectral band, band of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' (or simply light). The optical spectrum is sometimes considered to be the same as the visible spectrum, but some authors define the term more broadly, to include the ultraviolet and infrared parts of the electromagnetic spectrum as well, known collectively as ''optical radiation''. A typical human eye will respond to wavelengths from about 380 to about 750 nanometers. In terms of frequency, this corresponds to a band in the vicinity of 400–790 Terahertz (unit), terahertz. These boundaries are not sharply defined and may vary per individual. Under optimal conditions, these limits of human perception can extend to 310 nm (ultraviolet) and 1100 nm (near infrared). The spectrum does not contain all the colors that the human visual system can distinguish. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radio Spectrum
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio waves is strictly regulated by national laws, coordinated by an international body, the International Telecommunication Union (ITU). Different parts of the radio spectrum are allocated by the ITU for different radio transmission technologies and applications; some 40 radiocommunication services are defined in the ITU's Radio Regulations (RR). In some cases, parts of the radio spectrum are sold or licensed to operators of private radio transmission services (for example, cellular telephone operators or broadcast television stations). Ranges of allocated frequencies are often referred to by their provisioned use (for exampl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hanbury Brown And Twiss Effect
In physics, the Hanbury Brown and Twiss (HBT) effect is any of a variety of correlation and anti-correlation effects in the intensity (physics), intensities received by two detectors from a beam of particles. HBT effects can generally be attributed to the wave–particle duality of the beam, and the results of a given experiment depend on whether the beam is composed of fermions or bosons. Devices which use the effect are commonly called intensity interferometers and were originally used in astronomy, although they are also heavily used in the field of quantum optics. History In 1954, Robert Hanbury Brown and Richard Q. Twiss introduced the intensity interferometer concept to radio astronomy for measuring the tiny angular size of stars, suggesting that it might work with visible light as well. Soon after they successfully tested that suggestion: in 1956 they published an in-lab experimental mockup using blue light from a mercury-vapor lamp, and later in the same year, they appl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonon Noise
Phonon noise, also known as thermal fluctuation noise, arises from the random exchange of energy between a thermal mass and its surrounding environment. This energy is quantized in the form of phonons. Each phonon has an energy of order k_\textT, where k_\text is the Boltzmann constant and T is the temperature. The random exchange of energy leads to fluctuations in temperature. This occurs even when the thermal mass and the environment are in thermal equilibrium, i.e. at the same time-average temperature. If a device has a temperature-dependent electrical resistance, then these fluctuations in temperature lead to fluctuations in resistance. Examples of devices where phonon noise is important include bolometers and calorimeters. The superconducting transition edge sensor (TES), which can be operated either as a bolometer or a calorimeter, is an example of a device for which phonon noise can significantly contribute to the total noise.K.D. Irwin and G. C. Hilton (2005). Enss, C. ed"T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
