A quantum well infrared photodetector QWIP , is an infrared photodetector made from semiconductor materials which contain one or more quantum well s. These can be integrated together with electronics and optics to make infrared camera s for thermography . A very common well material is gallium arsenide , used with barrier material aluminium gallium arsenide . There are several companies world wide manufacturing infrared systems which use QWIPs. It is also considered a game changing technology in the field of within visual range air to air missiles where it can detect object far outside visual range of the pilot. External links http qwip.jpl.nasa.gov NASA qwip research Category Optical devices Category Image sensors Category Infrared imaging optics stub de Quantentopf Infrarot Photodetektor fr QWIP ... more details
Photosensors or photodetectors are sensors of light or other Electromagnetic radiation electromagnetic energy. There are several varieties ref cite journal doi 10.1063 1.2884264 title Study of residual background carriers in midinfrared InAs GaSb superlattices for uncooled detector operation year 2008 last1 Haugan first1 H. J. first2 S. first3 F. first4 B. first5 G. J. first6 W. C. journal Applied Physics Letters volume 92 pages 071102 ref optics Optical detectors, which are mostly quantum devices in which an individual photon produces a discrete effect. Chemical detectors, such as photographic plate s, in which a silver halide molecule is split into an atom of metallic silver and a halogen atom. The photographic developer causes adjacent molecules to split similarly. Photoresistor s or Light Dependent Resistors LDR which change electrical resistance resistance according to light intensity Photovoltaic cells or solar cell s which produce a voltage and supply an electric current when illuminated Photodiode s which can operate in photovoltaic mode or photoconductive mode Photomultiplier tubes containing a photocathode which emits electron s when illuminated, the electrons are then amplified by a chain of dynode s. Phototube s containing a photocathode which emits electron s when illuminated, such that the tube conducts a current proportional to the light intensity. Phototransistor s, which act like amplifying photodiodes. Optical detectors that are effectively thermometers, responding purely to the heating effect of the incoming radiation, such as pyroelectric detector s, Golay cell s, thermocouple s and thermistor s, but the latter two are much less sensitive. Cryogenic detectors are sufficiently sensitive to measure the energy of single x ray, visible and near infra red photons. ref cite book author Enss, Christian Editor title Cryogenic Particle Detection publisher Springer, Topics in applied physics 99 year 2005 isbn 3 540 20113 0 ref Charge coupled device s CCD , ... more details
Summary Concept of the photonic assisted all dielectric RF front end technology. An electro optic EO powered dielectric antenna captures the free space RF signal. The embedded optical link provides complete electrical isolation between the air interface and the electronic circuitry, which is located only after the photodetector PD . Licensing PD self date February 2009 ... more details
Orphan date February 2011 A Winston cone is a light collection device with a paraboloid parabolic shape and a reflective inner surface. It concentrates the light passing through a relatively large entrance aperture through a smaller exit aperture. The collection of incoming rays is maximized by allowing off axis rays to make multiple reflections before reaching the exit aperture. Winston cones are used to concentrate light from a large area onto a smaller photodetector or photomultiplier . Category Optical devices optics stub ... more details
Optical Sorting is a process of visually sorting a product though the use of Photodetector light sensors , Camera ref http www.woodheadpublishing.com en book.aspx?bookID 614&printer yes Detecting foreign bodies in food ref , or the Human eye ref Image Processing for the Food Industry , E. R. Davis World Scientific Publishing Co. Pte. Ltd. London, 2000 ref . In its simplest operation, a machine will simply see how much light is reflected off the object using a simple Photodetector such as a Photoresistor and accept or reject the item depending on how reflective it is light or dark . More sophisticated systems use Image processing to discriminate the colors of the object, often via a controlled Spectrum spectra of light, even beyond the visible spectrum into the IR and UV range. Shape detection is an evolving ability. The common method of removal is jets of compressed air, but others exist. The term Optical sorting also includes manual seeing and manipulating processes. http www.odenberg.com Odenberg Engineering , http www.lasersorter.com Visys , Satake Corporation , http www.bestsorting.com Best , and http www.buhlergroup.com 17217EN.asp Sortex are some companies that build Optical Sorting machines for the food sector to ensure consistent quality & safety. Further reading references optics stub Category Optics stubs Category Optics ... more details
Responsivity measures the input output gain of a detector system. For a system that responds linear ly to its input, there is a unique responsivity. For nonlinear system s, the responsivity is the local slope derivative . ref cite book title Multielement Detection Systems for Spectrochemical Analysis author Kenneth W. Busch, Marianna A. Busch publisher Wiley Interscience year 1990 isbn 0471819743 url http books.google.com books?id 9H0W1J Rku4C&pg PA371&dq responsivity&as brr 0&ei T4AdR8y4MaL6pwKkvZER&sig Y eF UkViCv9V7XkMViMRZOSlz4 ref In the specific case of a photodetector , responsivity measures the electrical output per optical input. Many common photodetectors respond linearly as a function of the incident power. Responsivity of a photodetector is usually expressed in ampere s per watt , or volt s per watt, of incident radiant flux radiant power . Responsivity is a function of the wavelength of the incident Electromagnetic radiation radiation and of the sensor properties, such as the bandgap of the material of which the photodetector is made. One simple expression for Responsivity R sub sub commonly used with photodetectors is listed below, where math eta math is the quantum efficiency conversion efficiency of photons to electrons of the detector for a given wavelength. math R lambda frac q h nu times eta approx frac lambda mu m 1.23985 times eta math The term responsivity is also used to summarize input output relationship in non electrical systems. For example, a neuroscientist may measure how neurons in the visual pathway respond to light. In this case, responsivity summarizes the change in the neural response per unit signal strength. The responsivity in these applications can have a variety of units. The signal strength typically is controlled by varying either intensity intensity response function or contrast contrast response function . The neural response measure depends on the part of the nervous system under study. For example, at the level of the r ... more details
Photoreceptor can refer to In anatomy cell biology Photoreceptor cell a photosensitive cell in the retina of vertebrate eyes Simple eyes in arthropods Ocellus , photoreceptor organ simple eye of invertebrates often composed of a few sensory cells and a single lens Eyespot apparatus microbial photoreceptor the photoreceptor organelle of a unicellular organism that allows for phototaxis In biochemistry Photoreceptor protein a chromoprotein that responds to being exposed to a certain wavelength of light by initiating a signal transduction cascade Photopigment an unstable pigment that undergoes a physical or chemical change upon absorbing a particular wavelength of light also see Photosynthetic pigment molecules involved in transducing light into chemical energy In technology Photodetector or photosensor a device that detects light by capturing photons Electronic Photoreceptor Sensor that converts solar energy into electric energy disamb cs Fotoreceptor de Fotorezeptor fr Photor cepteur ... more details
An opto electronic oscillator OEO is an optoelectronic Electric circuit circuit that produces repetitive electronic sine wave and or modulated optical continuous wave signals. An opto electronic oscillator is based on converting the continuous light energy from a pump laser to radio frequency RF and microwave signals. The OEO is characterized by having very high quality factor Q and Stability mathematics stability , as well as other functional characteristics that are not readily achieved with electronic oscillator s. Its unique behavior results from the use of electro optical E O and photonic components, which are generally characterized with high efficiency, high speed, and low Dispersion optics dispersion in the microwave frequency regime. Operation Most OEOs utilize the transmission characteristics of a modulator together with a fiber optic delay line to convert light energy into stable, Spectral purity spectrally pure RF microwave reference signals. Light from a laser is introduced into an E O modulator, the output of which is passed through a long optical fiber and detected with a photodetector . The output of the photodetector is Amplifier amplified and filtered and fed back to the electric port of the modulator. This configuration supports self sustained oscillations, at a frequency determined by the fiber delay length, the bias setting of the modulator, and the Bandpass filter band pass characteristics of the filter. It also provides for both electric and optical outputs. The conditions for self sustained oscillations include coherent addition of partial waves each way around the loop and a loop gain exceeding losses for the circulating waves in the loop. The first condition implies that all signals that differ in phase waves phase by some multiple of 2 from the fundamental signal may be sustained. Thus the oscillation frequency is limited only by the characteristic frequency response of the modulator and the setting of the filter, which eliminates all oth ... more details
about the optoelectronic component the optical component Optical switch The slotted optical switch , sometimes known as opto switch or optical switch but not to be confused with the optical component, is a device comprising a semiconductor photoemitter e.g., photodiode and photodetector mounted in a single package so that the photoemitter normally illuminates the photodetector, but an opaque object can be inserted in a slot between them so as to break the beam. Associated Electronic circuit circuit ry is provided which changes state when the beam is interrupted. For example, the carriage of a computer printer may be fitted with a projection which interrupts the beam of a slotted switch when it reaches the end of its travel, causing circuitry to react appropriately. This device uses the same basic components as an opto coupler , but is operated by manipulating the light path instead of the photoemitter input. The typical computer mouse with a ball uses two slotted opto switches to detect movement on the two axis. ref http books.google.com books?id Qq0CVfcAktUC&pg PA132&dq mouse opto switch&hl en&ei V9uZTM DB42OjAeLo1w&sa X&oi book result&ct result&resnum 4&ved 0CDkQ6AEwAw v onepage&q mouse 20opto 20switch&f false ref ref http books.google.com books?id NmVXZnx 3kC&pg PA22&dq mouse opto switch&hl en&ei NtqZTPDhO5S7jAfawsXxDw&sa X&oi book result&ct result&resnum 2&ved 0CC0Q6AEwAQ v onepage&q mouse 20opto 20switch&f false ref References reflist Category Optoelectronics electronics stub ... more details
This article is intended for those who are interested in the theoretical description of quantum process of photodetection. Readers who are interested in the applications of photodetection processes may want to read photodetector . In his historic paper, ref R. J. Glauber, Phys. Rev. 130, 2529 1963 . ref entitled The Quantum Theory of Optical Coherence, Roy J. Glauber set a solid foundation for the quantum electronics quantum optics enterprise. The experimental development of the optical maser and later laser at that time had made the classical concept of Coherence physics optical coherence inadequate. Glauber started from the quantum theory of light detection by considering the process of photoionization in which a photodetector is triggered by an ionizing absorption of a photon. In the quantum theory of radiation, the electric field operator in the Coulomb gauge may be written as the sum of positive and negative frequency parts math E mathbf r , t E mathbf r , t E mathbf r , t math where math E mathbf r , t E mathbf r , t dagger math One may expand math E mathbf r , t math in terms of the normal modes as follows math E mathbf r , t i sum j frac hbar omega j 2 1 2 hat a j mathbf varepsilon j e i mathbf k j cdot mathbf r omega j t math where math mathbf varepsilon j math are the unit vectors of polarization this expansion has the same form as the classical expansion except that now the field amplitudes math hat a j math are operators. Glauber showed that, for an ideal photodetector situated at a point math mathbf r math in a radiation field, the probability of observing a photoionization event in this detector between time math t math and math it t d it t math is proportional to math W I mathbf r , t d it t math , where math W I mathbf r , t psi mid E mathbf r , t cdot E mathbf r , t mid psi math and math psi rangle math specifies the state of the field. Since the radiation field is a quantum mechanical one, we do not know the exact properties of the incident light, ... more details
SPAD may refer to In aircraft manufacture Soci t Pour L Aviation et ses D riv s , also Soci t Provisoire des A roplanes Deperdussin and Bl riot SPAD, French aircraft manufacturer 1912 1921 SPAD VII , SPAD S.XII and SPAD S.XIII , French fighter planes of World War I produced by Soci t Pour L Aviation et ses D riv s A 1 Skyraider , nicknamed Spad , an attack aircraft 1950s and 1960s Simple Plastic Airplane Design , a type of radio controlled airplane In science Single pass albumin dialysis, a simple technique for liver dialysis Single photon avalanche diode , a solid state electronic photodetector Specific antipolysaccharide antibody deficiency, a type of primary immunodeficiency Other uses Special advisers in the United Kingdom Special adviser , informal shorthand for a post in the British Government Self propelled air defence, a self propelled anti aircraft weapon Signal passed at danger , when a train passes a signal on red A neologism describing an online classified ad designed to amass email addresses for the purpose of spamming Spam electronic spam ad The Malay language acronym of the Land Public Transport Commission Malaysia Land Public Transport Commission of Malaysia. disambig cs SPAD rozcestn k de SPAD es SPAD fr Spad pl SPAD ... more details
Spectrum of a deuterium lamp taken by pointing the light input port no fiber optic used of an Ocean Optics HR2000 spectrometer http www.oceanoptics.com toward the light produced by an ocean optics deuterium lamp. Balmer lines are marked with a D since this is deuterium not hydrogen deuterium alpha on the right at 656nm and the deuterium beta line on the left at 486nm. color of the text roughly corresponds to the color of the emitted light at these wavelengths. . The continuum emission on the far left from 400nm to 200 nm does not actually decrease in intensity from 250nm to 200nm and this is an artefact of the decreased CCD photodetector efficiency at those wavelengths. The continuum actually increases in intensity all the way down to about 165nm where the lyman band then dominates emission at lower vacuum UV wavelengths. Note that the tallest peak of the Fulcher band and the D alpha line are saturated to show more detail on less intense lines. Spectrum interpretation was done using information of balmer line location, hydrogen emission continuum information found at http www.iop.org EJ abstract 1367 2630 2 1 007 http ej.iop.org links rpdZlw1Sh 3PhXYF5L2xGVc2lqav5vpA nj0107.pdf and Fulcher band emission information found at http www.iop.org EJ abstract 0741 3335 46 4 006 . This spectrum is not calibrated for intensity. Spectrum taken by me. svg graph GFDL with disclaimers migration relicense ... more details
Relative intensity noise RIN , describes the instability in the power physics power level of a laser . The noise term is important to describe lasers used in fiber optic communication and LIDAR remote sensing. Relative intensity noise can be generated from Optical cavity cavity vibration, fluctuations in the laser gain medium or simply from transferred intensity noise from a laser pumping pump source . Since intensity noise typically is proportional to the intensity physics intensity , the relative intensity noise is typically independent of laser power. RIN typically falls off with frequency and is a kind of pink noise . Relative intensity noise is measured by sampling the output current of a photodetector over time and transforming this data set into frequency with a fast Fourier transform . RIN is usually presented as relative noise power in decibel s per hertz at one or several intensities. See also Shot noise External reference http www.rp photonics.com intensity noise.html Intensity noise in Encyclopedia of Laser Physics and Technology http www.rp photonics.com relative intensity noise.html Relative Intensity Noise in Encyclopedia of Laser Physics and Technology Category Noise Category Fiber optic communications Category Laser science optics stub ... more details
Photodetector QWIP is a digital sensor that is being utilised in numerous ways, not only by scientists ... Infrared LWIR Quantum Dot Infrared Photodetector QDIP Focal Plane Array Camera . Dr. Gunapala resides in the suburbs of Los Angeles, California. He hosted the Quantum Structure Infrared Photodetector ... more details
Unreferenced date November 2008 In physics and in electronic engineering , dark current is the relatively small electric current that flows through photodetector photosensitive devices such as a photomultiplier tube , photodiode , or charge coupled device even when no photon s are entering the device. It is referred to as reverse bias leakage current in non optical devices and is present in all diode s. Physically, dark current is due to the random generation of electron s and electron hole holes within the depletion region of the device that are then swept by the high electric field . The charge generation rate is related to specific crystallographic defect s within the depletion region. Dark current spectroscopy can be used to determine the defects present by monitoring the peaks in the dark current histogram s evolution with temperature. Dark current is one of the main sources for noise in image sensor s such as charge coupled device s. The pattern of different dark currents can result in a fixed pattern noise dark frame subtraction can remove an estimate of the mean fixed pattern, but there still remains a temporal noise, because the dark current itself has a shot noise . Category Electronic engineering Category Optoelectronics fr Courant d obscurit ru ... more details
Chip Vision Systems, April 1996 br 9 Laser Focus World Custom Photodetector Arrays Meet Design ... 14 P. Suni Photodetector Arrays for Optical Processing, Proc. of the SPIE, 1990 br 15 P. Suni et al. A Linear 1024 Element High Speed, Wide Dynamic Range CCD Photodetector Array, Proc. of the SPIE, 1989 br 16 U.S. Patent 4967249 Gain Compression Photodetector Array br 17 U.S. Patent 4958207 Floating Diode Gain Compression br 18 U.S. Patent 5602407 Switched CCD Electrode Photodetector br 19 U.S. Patent ... more details
otheruses refimprove date January 2011 An electric eye is a photodetector used for detecting obstruction of a light beam. An example is the door safety Door Door related accidents system used on garage door opener s that use a light transmitter and receiver at the bottom of the door to prevent closing if there is any obstruction in the way that breaks the light beam. The device does not provide an image only presence of light is detectable. Visible light may be used, but infrared radiation conceals the operation of the device and typically is used in modern systems. Originally systems used lamps powered by direct current or the power line altenrating curent frequency, but modern photodetector systems use an infrared LED light emitting diode modulated at a few kilohertz, which allows the detector to reject stray light and improves the range, sensitivity nd security of the device. Examples Highway vehicle counter In the 1930s an electric eye vehicle counter was introduced in the US using two IR lamps set apart so that only cars and not pedestrians would be counted. ref http books.google.com books?id dyYDAAAAMBAJ&pg PA36&dq Popular Science motor gun boat&hl en&ei NinuTNraIJ2KnAexu8T4Cg&sa X&oi book result&ct result&resnum 10&ved 0CFMQ6AEwCQ v onepage&q&f true Autos Are Counted By Electric Eye , January 1937, Popular Science ref First compact commercial unit Also, a compact type of electric eye was offered in 1931 that was enclosed in a small steel case and much easier to install compared to older models. ref http books.google.com books?id u IDAAAAMBAJ&pg PA398&dq Popular Mechanics 1931 curtiss&hl en&ei 2kTvTOz A6HfnQfR0 C7Cw&sa X&oi book result&ct result&resnum 3&sqi 2&ved 0CC8Q6AEwAg v onepage&q&f true Electric Eye And Relay Set Combined In Cabinet , March 1931, Popular Mechanics ref Automatic wrapping wachines In the 1930s an electric eye apparatus was developed to help a wrapping machine, wrap 82 boxes a minute. ref http books.google.com books?id u IDAAAAMBAJ&pg PA185 ... more details
In telecommunication , John R. Carson Carson s bandwidth rule defines the approximate Bandwidth signal processing bandwidth requirements of communications system components for a carrier wave carrier signal information theory signal that is frequency modulated by a continuous or broad spectrum of frequencies rather than a single frequency. Carson s rule does not apply well when the modulating signal contains discontinuities, such as a square wave. Carson s rule originates from John Renshaw Carson s 1922 paper. ref J.R. Carson, Notes on the theory of modulation , Proc. IRE , vol. 10, no. 1 Feb. 1922 , pp. 57 64. ref Carson s bandwidth rule is expressed by the relation math CBR 2 Delta f f m math where CBR is the bandwidth requirement, math Delta f math is the peak frequency deviation , and math f m math is the highest frequency in the modulating signal. For example, an FM signal with 5 kHz peak deviation, and a maximum audio frequency of 3 kHz, would require an approximate bandwidth 2 5 3 16 kHz. Carson s bandwidth rule is often applied to transmitter s, antenna radio antenna s, optical sources, receiver radio receiver s, photodetector s, and other communications system components. Any modulated signal will have an infinite number of sidebands and hence an infinite bandwidth but in practice all significant sideband energy 98 or more is concentrated within the bandwidth defined by Carson s rule. It is a useful approximation, but setting the arbitrary definition of occupied bandwidth at 98 of the power still means that the power outside the band is only about 17 dB less than the carrier inside math 10 log left frac 0.02 0.98 right math , therefore Carson s Rule is of little use in spectrum planning. References references FS1037C Leon W. Couch II , Digital and Analog Communication Systems, 6th Edition , Prentice Hall, Inc., 2001 . ISBN 0 13 081223 4 DEFAULTSORT Carson Bandwidth Rule Category Telecommunications terms Category Rules of thumb es Regla de Carson f ... more details
A rubidium standard or rubidium atomic clock is a frequency standard in which a specified hyperfine level hyperfine transition of electron s in rubidium 87 atoms is used to control the output frequency. They are the most inexpensive, compact, and widely used type of atomic clock , used to control the frequency of television station s, cellular base station cell phone base stations , in test equipment, and global navigation satellite system s like Global Positioning System GPS . Commercial rubidium clocks are less accurate than Cesium clock cesium atomic clock s which serve as Primary standard primary frequency standards , so the rubidium clock is a secondary frequency standard . However, rubidium fountains are currently being developed that are even more stable than caesium fountain clocks. All commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6 834 682 610.904 324 Hz. The amount of light from a rubidium discharge lamp that reaches a photodetector through a resonance cell will drop by about 0.1 when the rubidium vapor in the resonance cell is exposed to microwave power near the transition frequency . The crystal oscillator is stabilized to the rubidium transition by detecting the light dip while sweeping an Radio frequency RF frequency synthesizer synthesizer referenced to the crystal through the transition frequency. See also Atomic clock Caesium standard Hydrogen maser References NIST PD http tf.nist.gov general enc re.htm resonancefrequency FS1037C External links http tf.nist.gov general enc re.htm resonancefrequency NIST Time & Frequency A Z Glossary Resonance Frequency http www.npl.co.uk server.php?show ConWebDoc.1727 Secondary Representation of the SI Second http www.ptb.de en org 4 44 441 info2 e.htm PTB Unit of Time http tycho.usno.navy.mil clockdev RubidiumFountain.html USNO Rubidium Fountain Project http www.npl.co.uk science technology time frequency microw ... more details
Specific detectivity , or D , for a photodetector is a figure of merit used to characterize performance, equal to the reciprocal of noise equivalent power NEP , normalized to unit area and unit Bandwidth signal processing bandwidth . Specific detectivity is given by math D frac sqrt A cdot Delta f NEP math , where math A math is the area of the photosensitive region of the detector and math Delta f math is the effective noise bandwidth. Its common units are math cm cdot Hz 1 2 W math , also called the Jones in honour to R. Clark Jones who defined this magnitude. ref R. Clark Jones, Proc. IRIS 2, No. 1, 9 12 1957 ref ref R. C. Jones, Proposal of the detectivity D for detectors limited by radiation noise, J. Opt. Soc. Am. 50, 1058 1960 http www.opticsinfobase.org abstract.cfm?id 52167 LINK ref Given noise equivalent power can be expressed as a function of responsivity , noise spectral density math A Hz 1 2 math and noise bandwidth as math NEP frac S n cdot sqrt Delta f mathfrak R math , it s common to see Specific detectivity expressed as math D frac mathfrak R cdot sqrt A S n math . The unit Jones is now commonly used with the D figure of merit. References and footnotes div class references small style moz column count 1 column count 1 references div Category Physical quantities FS1037C Category Infrared imaging physics stub ... more details
File Sphalerite unit cell depth fade 3D balls.png thumb The crystal structure of aluminium gallium arsenide is Zincblende crystal structure zincblende . Aluminium gallium arsenide also aluminum gallium arsenide Aluminium Al sub x sub gallium Ga sub 1 x sub arsenic As is a semiconductor material with very nearly the same lattice constant as Gallium arsenide GaAs , but a larger bandgap . The x in the formula above is a number between 0 and 1 this indicates an arbitrary alloy between Gallium arsenide GaAs and Aluminium arsenide AlAs . The bandgap varies between 1.42 electron volt eV GaAs and 2.16 eV AlAs . For x 0.4, the direct bandgap bandgap is direct . The formula AlGaAs should be considered an abbreviated form of the above, rather than any particular ratio. Aluminium gallium arsenide is used as a barrier material in GaAs based heterostructure devices. The AlGaAs layer confines the electrons to a gallium arsenide region. An example of such a device is a quantum well infrared photodetector QWIP . It can also be used in 1064 nm Infra red laser diode s. Safety and toxicity aspects The toxicology of AlGaAs has not been fully investigated. The dust is an irritant to skin, eyes and lungs. The environment, health and safety aspects of aluminium gallium arsenide sources such as trimethylgallium and arsine and industrial hygiene monitoring studies of standard MOVPE sources have been reported recently in a review. ref Journal of Crystal Growth 2004 doi 10.1016 j.jcrysgro.2004.09.007 ref References references External links http www.ioffe.ru SVA NSM Semicond AlGaAs index.html Extensive site on the physical properties of aluminium gallium arsenide DEFAULTSORT Aluminium Gallium Arsenide Category Arsenides Category Aluminium compounds Category Gallium compounds Category Semiconductor materials Category III V compounds Category Light emitting diode materials ar de Aluminiumgalliumarsenid es Arseniuro de galio aluminio fr Ars niure de gallium aluminium ... more details
Refimprove date November 2010 Image Dynodes.jpg thumb right 300 px Dynodes in a photomultiplier tube. A dynode is one of a series of electrodes within a photomultiplier tube. Each dynode is at a more positive electrical potential than its predecessor. Secondary emission occurs at the surface of each dynode. Such an arrangement is able to amplify the tiny current emitted by the photocathode , typically by a factor of one million. Operation The electron s emitted from the cathode are accelerated toward the first dynode, which is maintained 90 to 100 V positive with respect to the cathode. Each accelerated photoelectron that strikes the dynode surface produces several electrons, that are then accelerated to the second dynode, which is held 90 to 100V more positive than dynode 1. For conventional dynode materials, such as BeO and MgO, a multiplication factor of 10 can normally be achieved by each dynode stage. ref Glenn F Knoll Radiation Detection and Measurement 3rd ed , 1999, P270, ISBN 0 471 07338 5. ref By the time this process has been repeated at each of the dynodes, 10 sup 5 sup to 10 sup 7 sup electrons have been produced for each incident photon, dependent on the number of dynodes. Naming The dynode is so named because it acts as a middle point between the photo cathode and the anode . References references See also Microchannel plate detector Photoelectric effect Particle detector Photodetector Category Electronic amplifiers Category Particle detectors ca Dinode de Dynode es D nodo fr Dynode it Dinodo lv Dinods nl Dynode pl Katoda wt rna ru ur ... more details
chembox ImageFile ImageSize ImageName ImageFile1 ImageSize1 ImageName1 OtherNames Cadmium diarsenide Section1 Chembox Identifiers ChemSpiderID 10678197 InChI 1 2As.3Cd q2 3 3 2 SMILES Cd 2 . Cd 2 . Cd 2 . AsH6 3 . AsH6 3 InChIKey PYIKGNIRLAMTQG UHFFFAOYAS CASNo 12006 15 4 EINECS 234 484 1 RTECS Section2 Chembox Properties Formula Cd sub 3 sub As sub 2 sub MolarMass 487.08 g mol Appearance solid, dark grey Density 3.031 Solubility decomposes in water MeltingPt BoilingPt Section3 Chembox Structure Coordination CrystalStruct Section7 Chembox Hazards EUClass FlashPt NFPA F 1 NFPA H 4 NFPA R 0 NFPA O W PEL 5 micrograms Cd m sub 3 sub LD50 no data Section8 Chembox Other OtherAnions OtherCations Cadmium arsenide cadmium Cd sub 3 sub arsenic As sub 2 sub is a crystal line semiconductor with a tetragonal structure in the II V family. It is a narrow gap semiconductor with an band gap energy gap of 0.14 Electronvolt eV . The electron mobility is very large at ambient temperature. It is a n type semiconductor n type intrinsic semiconductor . Cadmium arsenide can be prepared as amorphous semiconductive glass . Cadmium arsenide shows the Nernst effect . Cadmium arsenide is used in infrared detector s using Nernst effect, and in thin film dynamic pressure sensor s. It can be also used to make magnetoresistance magnetoresistors , and in photodetector s. http intl.ieeexplore.ieee.org xpl abs free.jsp?arNumber 781173 Cadmium arsenide can be used as a dopant for HgCdTe . External links http www.npi.gov.au database substance info profiles 17.html National Pollutant Inventory Cadmium and compounds Cadmium compounds Category Arsenides Category Cadmium compounds Category Semiconductor materials inorganic compound stub ja zh ... more details
A chalcogenide is a chemical compound consisting of at least one chalcogen ion and at least one more electropositive element. Although all group 16 element s of the periodic table are defined as chalcogens, the term is more commonly reserved for sulfide s, selenide s, and telluride s, rather than oxide s. photoconductivity Photoconductive chalcogenide glass es are used in xerography and television . Citation needed date December 2007 An optical processing chip using a chalcogenide as a photodetector has been developed by The University of Sydney with potential to speed up links between optical fibre networks and computers. ref http www.smh.com.au articles 2008 07 09 1215282927991.html Chip may speed up internet 100 times Deborah Smith for Sydney Morning Herald July 10, 2008 ref Examples Cadmium telluride Indium sulfide Zinc telluride Sodium selenide See also Phase change memory Chalcogen negative resistance External links http www.spacemart.com reports Tiny Chip Demonstrates Big Memory in Cosmos 999.html Tiny Chip Demonstrates Big Memory in Cosmos Michael P. Kleiman for Air Force Research Laboratory, Space Vehicles Directorate SpaceDaily Jul 27, 2006 http www.opticsinfobase.org abstract.cfm?URI oe 17 4 2182 Breakthrough switching speed with an all optical chalcogenide glass chip 640 Gbit s demultiplexing Michael Galili, Jing Xu, Hans C. Mulvad, Leif K. Oxenl we, Anders T. Clausen, Palle Jeppesen, Barry Luther Davis, Steve Madden, Andrei Rode, Duk Yong Choi, Mark Pelusi, Feng Luan, and Benjamin J. Eggleton Optics Express, Vol. 17, Issue 4, pp. 2182 2187 February 2, 2009 Maksym V. Kovalenko, Marcus Scheele, and Dmitri V. Talapin. Colloidal Nanocrystals with Molecular Metal Chalcogenide Surface Ligands . Science 324 12June2009 1417 1420 http www.theregister.co.uk 2010 02 12 earth abundant solar cells Big Blue boffins hatch dirt cheap solar cells The Register, 12 February 2010 References references Category Chalcogenides inorganic compound stub de Chalkogenide ko ... more details
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