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radiation Dictionary Terms

optical transition
The process by which an atomic system changes from one energy level to another by either the emission or absorption of visible, infrared or ultraviolet radiation.
point light source
1. With respect to angular subtense, a source of light, such as a star, that is very small. In a lab, a point source may be...
power flow equation
Optical fiber channel characterization scheme based on three assumptions; the discrete mode spectrum can be replaced by a...
nonselective sensor
A radiometric device or system having uniform responsivity relative to all of the radiation parameters, or relative to one...
principal E-plane
The plane in which the axis of maximum radiation and the electric vector are contained.
diffractometer
A measurement device used to study the structure of matter using the diffraction of electromagnetic radiation.
bolometer
A thermometric instrument used for the detection and measurement of radiant energy. Its essential component is a short...
phosphorography
A process used in pyrometry and photothermometry to create a photographic record of a surface's temperature gradients....
direct illumination
Light produced by visible radiation that moves from the light source to the object without reflection. With respect to...
Hypalon
E.I. duPont's trade name for a material used in the jacket of fiber optic cables. It is flame-retardant, thermally stable...
Doppler effect
The effect produced on a wave frequency because of the relative motion of a source or an observer. The radiation emitted...
metamerism
In colorimetry, the phenomenon in which spectrally different radiations produce the same color sensation for a given...
thermography
Thermography is a technique that involves the use of an infrared imaging device, called a thermal camera or infrared camera,...
Faraday configuration
Describes incident radiation propagating parallel to an externally applied magnetic field in magneto-optical experimentation.
actinometer
A device that measures the intensity of photochemically active radiation, particularly from the sun. One form of this...
near-ultraviolet light source
A light source, such as the sun or an incandescent lamp, that freely penetrates ordinary glass bulbs and emits in the...
atomic absorption spectrometer
An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical...
nonradiative transition
A nonradiative transition refers to a process in which an electron or an atom undergoes a change in its energy state without...
bend loss
The loss of optical power in an optical fiber because radiation escapes through its bends. The radiation loss caused by...
detector array
A detector array refers to a collection of individual detector elements arranged in a two-dimensional grid or matrix format....
quantum mechanics
The science of all complex elements of atomic and molecular spectra, and the interaction of radiation and matter.
arc light source
In present usage, especially for spectroscopic identification, an arc between electrodes that serves as a radiation source....
fluorescence
Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other...
soft radiation
Term applied to radiation composed of particles or photons that will not easily penetrate a material because of their low...
Brillouin scattering
Brillouin scattering is a phenomenon in physics where an incident electromagnetic wave (usually light) interacts with...
Stefan-Boltzmann law
The formula that indicates the total radiation at all wavelengths from a perfect blackbody. W Total = 5.67 x 10-12 T 4(W/cm2)
Cerenkov counter
An instrument that detects high-energy charged particles by analysis of the Cerenkov radiation that they emit.
balloon-borne astronomical system
Any instrument or system carried by a balloon to the upper atmosphere to measure and record atmospheric information, such as...
incandescence
The emission of light by thermal radiation of a temperature high enough to render the source of radiation visible.
quartz light source
A lamp with a quartz envelope that transmits radiation generally rich in the ultraviolet.
relative equilibrium
The steady state of temperature exhibited by a material that has absorbed and emitted radiation equally.
germanium crystal
Germanium crystal refers to a crystalline form of the element germanium (Ge), which is a metalloid and semiconductor...
guided mode
In an optical waveguide, a mode whose field decays monotonically in the transverse direction everywhere external to the core...
organic dye
Any organic substance, that when dissolved in appropriate liquid based solvents will absorb and emit electromagnetic...
coherent radiation
Radiation in which the phase relationship between any two points in the radiation field has a constant difference, or is...
adiabatic laser colorimetry
Method for studying absorption coefficients of low-loss materials, in which a sample is allowed to come to thermal...
fluorite
The optical form of the crystal fluorspar, calcium fluoride, that is utilized for its low optical dispersion, its low...
infrared instrument
Any of the photoelectric and thermal detectors, spectrographs and monochromators, thermographs, scanners, amplifier tubes,...
infrared light-emitting diode
An infrared light-emitting diode (IR LED) is a semiconductor device that emits infrared light when an electric current...
hyperspectral resolution
Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a...
gray scales
Transparencies that represent progressive steps in the amount of transmitted radiation for administering predetermined...
quartz spectrograph
A spectrograph used to detect radiation in the range of the ultraviolet in the electromagnetic spectrum. It is made up of...
infrared microscope
A type of microscope that uses radiation in the infrared region to illuminate objects that are opaque to visible radiation....
infrared photomicrography
Photographic recording that uses infrared radiation as the light source to form an image of a microscopic object and a...
polarimetric analysis
The determination of a substance's identity or quantity through the analysis of its optical rotation. For example, the...
step response
The observed time dependence of the transmittance of a step of radiation through a given medium.
direct-line fluorescence
With respect to atomic fluorescence spectroscopy, the fluorescence that is emitted by an atom at a spectral line of a...
full width half maximum
Full width half maximum (FWHM) is a measure of the extent of a function. Given by the difference between the two extreme...
Biberman factor
Mathematical compensation for the nonhydrogenic behavior of recombination radiation levels of gases, based on the quantum...
directed energy
Directed energy refers to a type of energy that is emitted and transferred in a controlled direction. The term is often...
haze filter
A filter, used in photography, that absorbs the ultraviolet and extreme blue violet radiation scattered by atmospheric haze.
x-ray detector
One of various types of fluorescent screens used to detect x-ray radiation. Photographic film is mildly sensitive to x-rays,...
infrared optic
Infrared optics refer to optical components and systems designed to manipulate and control infrared (IR) light, which lies...
nonperiodic radiation
Irregular waves; e.g., light waves, having little coherence and a broad spectrum of frequencies.
ultraviolet fiber optics
Ultraviolet (UV) fiber optics refers to optical fibers that are designed and optimized for the transmission of ultraviolet...
engram
A hologram produced by a pair of radiation beams, each carrying information.
thermograph
The instrument used to collect thermal radiation information on an object by scanning. It consists basically of a detector,...
thermomagnetic imaging
The production of an image on a magnetic film that is exposed to infrared radiation and heated to a point above Curie...
photovoltaic effect
The generation of a difference in electric potential between two electrodes when radiation is incident on one of them.
scintillation crystal
A scintillation crystal, also known simply as a scintillator, is a material that emits light when it interacts with ionizing...
spectrobolometer
A combination spectrometer and bolometer that is designed to measure a narrow band of radiation from a star.
laser
A laser, which stands for "light amplification by stimulated emission of radiation," is a device that produces coherent and...
radiation detector
Any of the many devices used to detect the presence of radiation from a specific region of the electromagnetic spectrum.
solar absorber
A substance capable of converting solar radiation into thermal energy.
near-infrared camera
A near-infrared (NIR) camera is an imaging device designed to capture images in the near-infrared region of the...
cold cathode
A cathode that emits electrons, not with the influence of heat radiation, but by means of a high-voltage gradient at its...
curing
The use of chemicals or radiation to induce a desired change in a substance; e.g., some optical adhesives are set by...
vibrational transition
A vibrational transition refers to a change in the vibrational energy of a molecule. Molecules consist of atoms that are...
sensitivity
In a radiation detector, the ratio of the output to the input signal.
filter
1. With respect to radiation, a device used to attenuate particular wavelengths or frequencies while passing others with...
free-electron laser
A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a...
cold mirror
A mirror whose coating serves to reflect visible radiation while transmitting the infrared.
x-radiography
Radiography using the emission of x-rays to form an image of the structure penetrated by the radiation.
laser eyewear
Usually consists of a set of filters that attenuate specific wavelengths but transmit as much visible radiation as possible.
radiation-monitoring film
The film used in photographic dosimetry to record the types and amounts of ionizing radiation, such as x-rays and gamma...
thermogram
Also known as analog thermogram. The resultant photograph, illustrating, in tones ranging from black to white, the spatial...
solid-state lamp
An electroluminescent semiconductor that emits low intensity radiation in the green or red regions. Used as an indicator...
accessible radiation
Electromagnetic radiation present upon the open aperture of the source within an operating environment.
cathodoluminescence
Light produced when a metal is bombarded with high-velocity electrons causing small amounts of the metal to vaporize and...
ion laser
A laser in which the transition involved in stimulated emission of radiation takes place between two levels of an ionized...
photoradiation therapy
invisible light filter
A filter that transmits infrared and ultraviolet but is opaque to visible radiation.
xerography
A printing process of electrostatic electrophotography that uses a photoconductive insulating medium, in conjunction with...
maximum permissable exposure
The maximum level of laser radiation that a person may be exposed to without adverse biological effects.
sensor
1. A generic term for detector. 2. A complete optical/mechanical/electronic system that contains some form of radiation...
monoergic
Pertaining to radiation or particle emission, whereby the emission is produced with minimal energy spread.
terahertz
Terahertz (THz) refers to a unit of frequency in the electromagnetic spectrum, denoting waves with frequencies between 0.1...
fluorescence quenching
The suppression of fluorescence by absorption of the stimulating radiation.
translucent
Pertaining to materials having the property of reflecting a part and transmitting a part of the incident radiation.
narcissus
A defect in infrared systems that appears as a dark circular area on a displayed image, caused by radiation reflecting into...
photoconductive effect
The alteration of electric conductivity produced by the absorption of varying amounts of radiation composed of photons.
intrabeam viewing
With respect to laser radiation, the subjection of the human eye to all or a portion of the laser beam.
saturation
1. The decrease of the absorption (or gain) coefficient of a medium near some transition frequency when the power of the...
monochromatic
Composed of one color; having only one wavelength of radiation.
black light
Radiation from the invisible (usually ultraviolet) region of the spectrum.
luminescent fiber
Fiber that emits luminescent radiation excited by ultraviolet, x-ray or high-energy particles.
deflection
Any bending of a wave of radiation away from its expected path, as, for example, by diffraction or by a magnetic field.
fluorescence photography
The photographic recording of a subject that exhibits luminescence only for an extremely short time (10-8 s) after the...
spatial filter
1. Generally, an emulsion mask having a clean annular region in an otherwise opaque region. It is designed to eliminate...
Mossbauer effect spectroscopy
Spectroscopy characterized by the Mossbauer effect - recoilless emission and absorption of nuclear gamma radiation- which...
barium fluoride
A relatively hard crystal, highly resistant to excessive energy radiation, that is frequently used for optical windows,...
resonance radiation
That radiation emitted by an atom or molecule that has the same frequency as that of an incident particle; e.g., a photon....
rad
A unit of energy absorbed from ionizing radiation, equal to 100 ergs per gram of irradiated material.
laser ceilometer
A device used for measuring the height of clouds from a position on the ground. Measurement technique uses a vertically...
radiation
The emission and/or propagation of energy through space or through a medium in the form of either waves or corpuscular...
photoelectric control
The control of an instrument or electrical circuit by the current produced by varying radiation incident to a photoelectric...
active region
The layer of material in a laser diode from which the optical radiation is emitted; light producing region
photoelectric emission
The electron emission from a substance or instrument whose surface has been bombarded by a suitable amount of radiation.
undulator magnet
A device used in a free-electron laser to convert the electron-beam's energy into microwave laser radiation by creating a...
photographic dosimetry
The use of photographic emulsions to detect and determine the amounts of ionizing radiation, such as x-rays and gamma rays,...
spectroscope
In a general sense, any one of a class of instruments used to disperse radiation, visible or invisible, into its component...
gray
1. A measure of absorbed dose, equal to the energy imparted by ionizing radiation to a mass of matter corresponding to 1 J...
laser plasma
A plasma produced by the interaction of an intense laser pulse with a material surface. Production of ionized particle with...
photomultiplier tube
A photomultiplier tube (PMT) is a highly sensitive vacuum tube that detects and amplifies low levels of light. It is widely...
snooperscope
An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an...
silicon cell
A solid-state device, composed of silicon, that is used to convert radiation into electrical energy.
Hertz effect
The ionization and spark emission due to exposure to ultraviolet radiation.
radiant heat
Infrared radiation emitted from a source that is not heated sufficiently to give off visible radiation.
laser detector
Device that operates by interaction of incident radiation with semiconductor based material in order to produce an...
ultraviolet photoemission spectroscopy
A technique for measuring the energy spectrum of electrons emitted during the absorption of ultraviolet radiation. This...
mask spectrometer
Instrument that uses absorption spectroscopy to detect gases in planetary atmospheres. Dispersed incoming radiation is...
solar laser
A laser pumped by solar radiation focused by mirrors.
spectrometer
A kind of spectrograph in which some form of detector, other than a photographic film, is used to measure the distribution...
radiation trapping
That process by which radiation spontaneously emitted by a volume of optical materials is resonantly reabsorbed within the...
fiber-coupled photoconductive antenna
A fiber-coupled photoconductive antenna (FCPA) is a type of optoelectronic device that combines a photoconductive antenna...
covered groove
A technique used in integrated optics where a groove is cut on a substrate surface and covered by a thin film to facilitate...
medium
Any substance or space through which electromagnetic radiation can travel.
circular scanning
Scanning characterized by the generation of a plane or right circular cone with a vertex angle of about 180° by the...
thermal dissociation
A technique for detecting free radicals by their electronic spectra. The material to be studied is placed in a...
FTIR spectrometer
FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of...
slit
An aperture, usually rectangular in shape, with a large length-to-width ratio, and a fixed or adjustable shape through which...
solar battery
A series of solar cells arranged to collect solar radiation and to generate a given amount of electrical energy.
mid-wave infrared
MWIR stands for mid-wave infrared, referring to a specific range of wavelengths within the infrared spectrum. Infrared...
spin-flip Raman laser
A semiconductor laser that operates in the infrared and that is pumped with strong pulses of radiation from a second laser....
high-voltage electron microscope
An imaging device whose technology contributes three specific advantages: ability to study large solid specimens that...
recombination radiation
The radiation emitted in semiconductors when electrons in the conduction band recombine with holes in the valence band. If...
gamma radiography
Radiography using the emission of gamma rays to form an image of the structure penetrated by the radiation.
Marx effect
The decrease in the energy of a photoelectric emission as a result of the simultaneous incidence of radiation having lower...
radiant energy
The energy passed on as electromagnetic radiation; e.g., radio, heat or light waves.
annihilation radiation
Gamma ray radiation released when matter and antimatter, such as electron and positron, unite and eliminate each other,...
infrared jamming
A countermeasure used against heat seeking missiles to reduce their effectiveness. Normally it involves the emittance of...
photopolymerization
A process in which a mixture of one or more monomers, plus a catalyst, polymerize under exposure to light radiation....
radiation pattern
Relative power distribution as a function of position or angle.
extended source
A radiation source that, unlike the point source, can be resolved by the naked eye into a geometrical image.
angstrom
An angstrom, symbolized by the Ångström or Å, is a unit of length used to express atomic and molecular...
bulk nonreciprocal device
A device that functions throughout the continuous radiation of a linearly polarized plane wave, and whose nonreciprocity...
double-beam spectrophotometer
A spectrophotometer in which the beam emitted by the radiation source is split into beams that travel through the sample and...
infrared absorption
Infrared radiation absorbed by crystals as a result of the excitation of lattice vibrations in which ions having opposite...
surface reflection
Also known as Fresnel reflection. That portion of the incident radiation that is reflected from the surface of a refractive...
Mie scattering
Mie scattering, named after the German physicist Gustav Mie, refers to the scattering of electromagnetic radiation (such as...
Rayleigh line
That element of a spectrum line in scattered radiation having a frequency equal to that of the corresponding incident...
channel electron multiplier
A photoelectric detector consisting of a glass tube internally coated with a low conductance material. Voltage applied along...
erythema
Localized redness of skin due to congestion of capillaries; a common result of overexposure to laser radiation.
infrared light source
An infrared light source is a device that emits light in the infrared spectrum, which lies beyond the visible spectrum of...
cobalt glass
Glass that transmits near-ultraviolet radiation but is opaque in the visible region. Also known as woods glass.
spectroradiometer
A spectroradiometer is a device used to measure the intensity of light at different wavelengths across the electromagnetic...
negative-refraction metamaterial
An artificial material, engineered to have a negative refractive index value, such that light or any other form of...
ondoscope
A glow discharge tube placed on an insulating rod to detect the presence of high-frequency radiation in the vicinity of a...
Josephson effect
Characteristic of radiation detectors that produce energy that is similar to the energy of superconductive gaps when...
Mills cross (telescope)
The Mills Cross telescope is a two dimensional radio telescope in which the two antenna arrays are positioned perpendicular...
ionizing radiation
Generally, any radiation that can form ions, either directly or indirectly, while traveling through a substance.
infrared thermistor
A thermistor that uses a semiconductor that is sensitive to infrared radiation to measure the radiation's intensity.
three-level laser
A laser having a material, such as ruby, that has an energy state structure of three levels: the ground state (1) wherein...
incomplete radiator
A thermal source that emits less radiation than a blackbody under identical temperature conditions.
Lyman-alpha radiation
The hydrogen-derived, ultraviolet radiation running from 1216 to 512 A, discovered by Theodore Lyman in 1914.
radiation temperature
The temperature of a complete radiator that has a total radiant emittance identical to that of an unknown resource.
refracted wave
A wave of radiation that has undergone refraction.
beta radiation
The high-speed electrons and positrons emitted by radioactive materials.
attosecond-pump attosecond-probe spectroscopy
Attosecond-pump attosecond-probe spectroscopy (APAP) is an advanced technique in ultrafast spectroscopy that allows...
emission line
The line or lines emitted by an element when its radiation particles travel from one energy level to another.
InGaAs photodiode
An InGaAs photodiode refers to a photodetector device that is constructed using a semiconductor material composed of a...
laser absorption spectroscopy
An experimental research technique by which absorbed or unabsorbed radiation is analyzed in order to characterize and...
extraterrestrial radiation
Radiation that is emitted by a source outside the Earth and its atmosphere.
Stokes line
A line of the Raman spectrum that fulfills Stokes' law because it possesses a wavelength that is greater than the radiation...
infrared radiation source
Any object that emits radiation of a wavelength lying between about 0.75 to 1000 µm. A calibrated secondary source...
aperture
An opening or hole through which radiation or matter may pass.
ablation threshold
The minimum energy required to induce atomic and molecular separation or displacement due to incident intense laser...
threshold wavelength
The greatest wavelength of radiation for a specified surface for the emission of electrons.
fluorescent screen
A fluorescent screen refers to a phosphorescent or fluorescent-coated surface that emits visible light when exposed to other...
infrared detector
An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible...
Geiger counter
Also called Geiger-Müller counter. An instrument designed to detect and measure radioactivity through the use of a...
far-ultraviolet radiation
That radiation characterized by wavelengths ranging from 0.2 to 0.3 µm in the electromagnetic spectrum.
astronomy
The scientific observation of celestial radiation that has reached the vicinity of Earth, and the interpretation of these...
antiguide
A waveguide that has a core with a lower refractive index than the refractive index of the cladding. This structure can...
electrodynamics
The study of the generation of electromagnetic power by radiation from high-energy beams.
intrinsic detector
A photodetector composed of a photoconductive material that, when exposed to radiation, conducts without the aid of added...
Bohr's frequency relation
The law given by the formula: that is, the frequency of radiation emitted or absorbed by a system when E2 and E1...
fluorescence spectroscopy
The spectroscopic study of radiation emitted by the process of fluorescence.
heat lamp
A lamp designed to emit a large amount of infrared radiation; used in applications requiring heat.
notch filter
Also referred to as a band-stop or band rejection filter; a notch filter is a filter that is designed to screen out a very...
superradiance
Directional and coherent radiation pulses that result from an ensemble of coherently prepared states in an optical medium.
dual-wavelength spectrophotometry
Spectrophotometry in which radiation of two separate wavelengths, usually one in an absorption band and the other not, pass...
radiation-shielding windows
Plates of glass containing as many heavy metal oxides as can be dissolved in the glass without causing devitrification. The...
pumping radiation
Radiation used to excite an optical or laser material to a higher energy level. See optical pumping.
mode
1. The characteristic of how light propagates through a waveguide that can be designated by a radiation pattern in a plane...
radiopaque
Incapable of being penetrated by any form of radiation.
transmission limit
A restricting wavelength above or below which a specified form of radiation is totally almost absorbed by a specified medium.
inverse bremsstrahlung
Collisional absorption of energy that occurs in inertial confinement fusion systems when hydrodynamic expansion of the...
photonic cavity
A photonic cavity, also known as an optical cavity, is a structure that confines electromagnetic radiation within a certain...
spiral scanning
A scanning process in which the greatest amount of radiation determines part of a spiral motion rotating in one direction.
packet
The finite amount of electrical charge generated in response to incident radiation and transferred from one storage element...
infrared spectroscopy
The measurement of the ability of matter to absorb, transmit or reflect infrared radiation and the relating of the resultant...
cadmium red line
The narrowest line of the cadmium spectrum; the red line has the purest radiation.
Faraday rotation
The effect discovered by Faraday in 1845 whereby nonoptically active materials or substances become capable of rotating the...
magneto-optics
Magneto-optics refers to the study and manipulation of the interaction between magnetic fields and light (electromagnetic...
mid-infrared camera
A mid-infrared camera is a type of imaging device designed to capture images in the mid-infrared (mid-IR) spectral range,...
vacuum ultraviolet detector
A device that serves to detect the presence of vacuum ultraviolet radiation. It may be photographic film, a thermopile, ion...
multichannel spectral analyzer
A spectrometric instrument that detects radiation simultaneously in multiple channels, sorts it spectrally from the deep...
photoconductive antenna
Photoconductive antenna (PCA) is a semiconductor element that generates or detects high-frequency electromagnetic signals....
harmonic wave analyzer
An instrument designed to calculate the amplitude and phase of the different harmonic elements of a radiation wave utilizing...
exciter filter
In ultraviolet and fluorescence photography, the term applied to the filter used in the photographic system and with the...
phototherapy
Phototherapy is a medical treatment that involves the use of light to treat various conditions, particularly those related...
Planck's law
A fundamental law of quantum theory which states that the discrete quanta of energy transfers associated with...
actinism
The creation of a chemical reaction in a substance when radiation is directed to it.
ultraviolet lens
A microscope used either to detect selective absorption of various wavelengths by the specimen or to achieve increased...
radiac
An acronym for radioactive detection, identification and computation. The term refers to the detection and measurement of...
spectral response
Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.
scatterplate
A flat plate having its surface formed into a random pattern by abrasives. Radiation wavelengths that are longer than the...
calorescence
The production of visible light by infrared radiation whereby the light is produced by heat and not by any direct change in...
glass dosimeter
A device that detects and measures the quantity of exposure to nuclear radiation. It uses a special glass rod that...
heat-transmitting filter
A filter that allows heat radiation from an incident beam to pass without absorption or reflection.
graser
An acronym of gamma ray amplification by stimulated emission of radiation. It is a gamma ray laser that operates between...
terahertz spectrometer
A terahertz spectrometer is a scientific instrument used to measure and analyze the properties of materials in the terahertz...
solar constant of radiation
Solar radiation intensity existing in free space at the mean solar distance of the Earth. Commonly expressed in g cal...
laser dazzle system
Visible laser radiation, often optically expanded and collimated, used to induced temporary blindness from within a walking...
linear energy transfer
The transfer of energy lost by radiation to the body, relative to the loss of energy per unit of path traveled.
Stokes' law
Relative to radiation wavelength, the law that states that the wavelength of luminescence stimulated by radiation always...
Cerenkov radiation
The radiation produced when a charged particle traverses a medium that has a refractive index considerably greater than...
Golay cell
A thermal radiation detector consisting of a small cell with a blackened plastic front face that bulges slightly when heat...
x-ray image spectrography
Irradiation of a cylindrical crystal with an x-ray beam resulting in Bragg diffraction that produces a slightly enlarged...
infrared phosphor
A phosphor, such as sulfide or selenide, that can be excited to luminescence by incident infrared radiation simultaneous to...
blackbody
An ideal body that completely absorbs all radiant energy striking it and, therefore, appears perfectly black at all...
scintillation detector
A scintillation detector is a radiation detection device that utilizes scintillation crystals to detect and measure ionizing...
partial coherence theory
Totally coherent radiation is produced by a purely monochromatic point source. In the real world the energy will have a...
echelette grating
A diffraction grating with lines and grooves formed so as to concentrate the radiation of a particular wavelength into one...
self-absorption
In optical emission spectroscopy, the reduction in radiant power in the central portion of spectral lines arising from the...
irradiation
Application of radiation to an object.
reflective
The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of...
arc flash
An arc flash is a sudden release of electrical energy due to an electric arc — a continuous, high-current discharge of...
detector
1. A device designed to convert the energy of incident radiation into another form for the determination of the presence of...
antibleaching
Characteristic of an absorber in the IR region, whereby absorption increases as a direct function of the intensity of the...
coded disc
A reticle carrying patterns of various forms that can be rotated in an optical beam to cause variations in the intensity of...
flame spectrum
The emission spectrum formed by the radiation from a sample that has been evaporated by a nonluminous flame.
collateral radiation
Category inclusive of all radiation that is incited electronically, except laser radiation, as a function of the application...
forward-looking infrared
A night-vision device that uses one or more infrared transducers to scan a scene in the 3- to 5-µm or 8- to...
actinic glass
Glass designed to absorb most infrared and ultraviolet radiation while transmitting most of the visible region.
ultrasonic detector
A mechanical, electrical, thermal or optical detector designed to identify and measure ultrasonic radiation.
gamma ray
The spontaneous emittance of electromagnetic radiation by the nucleus of certain radioactive elements during their quantum...
semitransparent photocathode
A photocathode that receives radiation from one side and emits a photoelectric current from the opposite side.
far-infrared maser
A gas maser that is capable of producing radiation in the far-infrared region of the spectrum.
end-fire coupling
End-fire coupling refers to a method of coupling energy into or out of a waveguide, transmission line, or antenna, where the...
black surface enclosure
An enclosure whose walls are coated to absorb completely all radiation striking them.
luminous exitance
The total luminous flux given out per unit area; i.e., the sum of the luminous emittance and any radiation that is reflected...
photochromic
Photochromic refers to a property exhibited by certain materials, typically organic compounds or dyes, which undergo...
Kirchhoff's law
For any point on a thermal radiator, at thermal equilibrium and for each wavelength, the emissivity in any direction is...
centerburst
In an interferogram, an intense portion of the recording that corresponds in size to the amount of infrared radiation...
free-carrier absorption
The phenomenon whereby an electron within a band absorbs radiation by transferring from a low-energy level to an empty...
resonance spectrum
The fluorescent emission spectrum emitted by certain substances following the irradiation of one of these substances with...
Angstrom compensation pyrheliometer
A system used for measuring direct solar radiation.
photosensitizer
A substance that increases a material's sensitivity to electromagnetic irradiation. In photodynamic therapy, a drug used to...
ultraviolet lamp
A type of lamp that emits a high quantity of ultraviolet radiation. This may be an arc lamp encased in a bulb of a glass...
spectral pyrheliometer
Any pyrheliometer that has a filter placed over its sensor to limit the range of solar radiation it will detect; used to...
reflecting microscope
A microscope that uses a reflecting objective; often used with ultraviolet or infrared radiation.
ultraviolet lens
A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz, calcium fluoride, lithium...
amplified spontaneous emission
Broadband radiation emitted by a laser that does not transmit through the optical element. It can be removed by filtering.
spectrogrammetric reading equipment
Spectra can be conveniently recorded on photographic film or plates. The portions that are occupied by regions of the...
photon drag detector
An infrared detector in which radiation passes through a doped germanium crystal, creating a voltage drop that can be...
infrared photography
The photographic recording of images on a medium sensitive to infrared radiation, using a source capable of emitting in the...
calorific rays
Name originally given to the sun's infrared radiation by Sir William Herschel in his Philosophical Transactions of 1800.
reflectivity
The ratio of the intensity of the total radiation reflected from a surface to the total incident on that surface.
photochromism
The reversible change in the absorption spectrum of certain compounds upon irradiation with a given wavelength of light.
photochromatic compound
A chemical compound that exhibits a reversible change in its absorption spectrum upon irradiation with given wavelengths of...
photodiode
A two-electrode, radiation-sensitive junction formed in a semiconductor material in which the reverse current varies with...
infrared camera
An infrared camera, also known as a thermal imaging camera or IR camera, is a device that captures and visualizes the...
radiation dosimetry
The detection and measurement of nuclear and x-ray radiation.
broadside radiation
Radiation that occurs perpendicular to the plane of the radiation device.
solar furnace
An optical system that is designed to produce a high temperature in a specified area by the optical direction and...
image converter
An electron tube that employs electromagnetic radiation to produce a visual replica of an image produced on its cathode....
radiation counter
An instrument used to recognize and identify incident radiation by the ionizing or stimulating properties of the radiation.
heterochromatic light
Radiation consisting of more than a single wavelength in the visible region of the spectrum.
photochemical
The term photochemical pertains to chemical processes or reactions that are initiated or influenced by the absorption of...
Kubelka-Munk theory
A two-flux theory in which the radiation is assumed to be composed of two oppositely directed radiation fluxes through a...
kinetic cooling
An atmospheric nonlinear process unique to CO2 laser wavelengths, whereby CO2 absorbs 10.6-µm radiation and the CO2...
lossy medium
A medium that scatters or absorbs radiation that passes through it.
Compton scattering
The phenomenon observed by A.H. Compton in 1923 -- that some scattered radiation possesses a longer wavelength and...
Wien's displacement law
The formula that gives the wavelength of maximum spectral radiant emittance of a perfect blackbody: λmax =...
actinic radiation
Electromagnetic energy that is capable of producing photochemical activity.
plasmonics
Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free...
equalized-response densitometer
A densitometer having a receiver that indicates when a desired radiation level has been attained.
global radiation
The total radiation, both solar and diffuse sky, that is incident to a unit's horizontal surface.
spectrum light source
A lamp that yields a nonluminous flame; used in the spectroscopic analysis of radiation emitted by a substance placed in the...
light source
The generic term applied to all sources of visible radiation from burning matter to ionized vapors and lasers, regardless of...
spectral signature
A spectral signature, in the context of remote sensing and spectroscopy, refers to the unique pattern or characteristic...
solar radiation
Radiation from the sun that is made up of a very wide range of wavelengths, from the long infrared to the short ultraviolet...
term coherence
A synonym for spatial coherence. See spatially coherent radiation.
Gudden-Pohl effect
The light flash that occurs when an electrical field is applied to a phosphor already excited by ultraviolet radiation.
spectral luminous efficacy
Ratio of the luminous flux in a beam of radiation to the spectral radiant flux in the same beam at a given wavelength.
overexposure
The improper exposure of a radiation-sensitive medium that results when there is too much radiation exposing the medium, or...
image intensifier
An image intensifier, also known as an image intensification tube or image intensification device, is a specialized...
Herschel effect
The decrease in effect in developable density on a photographic plate formed by a second exposure to radiation having a...
illuminant
Source of radiation defined or specified by its spectral power distribution.
infrared alarm system
A system that uses infrared detectors and related instrumentation to determine when abnormal amounts of infrared radiation,...
Nernst glower
A Nernst glower, also known simply as a Nernst lamp or Nernst filament, is a type of incandescent lamp or radiant heater...
reflection
Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface;...
scattering
Change of the spatial distribution of a beam of radiation when it interacts with a surface or a heterogeneous medium, in...
infrared reflector
An optical component coated to reflect infrared radiation. Gold, silver and aluminum are typical coating materials.
emissive power
The emissivity of a body times the emissive power of a blackbody at the same temperature. For a blackbody, it is the total...
radiophotoluminescence
The luminescence displayed when particular minerals are irradiated with β-rays and g-rays, after being exposed to...
grating
A framework or latticework having an even arrangement of rods, or any other long narrow objects with interstices between...
microbending loss
Transmission loss in optical fibers caused by packaging processes; it is considered a power-coupling effect from the guided...
optical clock
An optical clock is a highly precise and advanced timekeeping device that relies on the oscillations of electromagnetic...
laser dye
Class of organic dyes that emit coherent radiation over a wide spectral range.
epitaxial equipment
Epitaxial equipment refers to a set of specialized tools and systems used in the process of epitaxy, which is the growth of...
emitter
A source of radiation.
air dose
A quantitative measure of the amount of radiation given off by an instrument, expressed in roentgens per unit of free air.
dosimeter
A device used to detect and measure the quantity of exposure to nuclear or x-ray radiation, and dependent on the fact that...
infrared bolometer
A superconducting bolometer, operating at very low temperatures, that is used to detect infrared radiation.
infrared spectrophotometer
A spectrophotometer having a prism or, more frequently, a grating for the study and recording of infrared spectra. It...
electron spectroscopy
The theory and interpretation of spectra produced by the electron emissions of substances after their irradiation by x-rays.
vacuum ultraviolet radiation
Radiation whose spectrum runs between 100 and 300 nm. Any work with these wavelengths requires evacuated equipment.
atmospheric window
A range of wavelengths within which radiation transmitted through the atmosphere suffers relatively little absorption by...
lead selenide cell
A thin-film photoconductive cell that is sensitive to the infrared region. The photosensitive material of the cell is...
Er:YAG laser
An Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet...
nonlinear optical crystal
An optical crystal that possesses a strong nonlinear dielectric response function to optical radiation. A material with a...
synchrotron radiation
Radiation emitted by electrons when they travel in circular orbits at speeds close to that of light. Synchrotron radiation...
radiology
The study of radioactive substances and high-energy radiations such as x-rays and g-rays.
Doppler broadening
The spreading of potentially equal radiation frequencies that results in broadening of the spectral line. This effect is...
Fresnel zone plate
A zone plate in which the zones are alternately transparent and opaque to specific radiation, and coarse enough so that no...
stimulated emission
Radiation similar in origin to spontaneous emission but determined by the presence of other radiation having the same...
flash photographic density filter
A filter, partially opaque to near-ultraviolet, visible and infrared radiation, that may be made by exposing and processing...
aperture imaging
The formation of an image by a pinhole aperture that transmits radiation, such as gamma radiation.
transverse scattering
The method for measuring the index profile of an optical fiber or preform by illuminating it coherently and transversely to...
photoelectric constant
The constant that, multiplied by the frequency of the radiation-producing emission of photoelectrons, determines the amount...
Touschek effect
Effect whereby two electrons lose synchronism with the accelerating field and are lost during synchronous radiation. The...
maser
An acronym for microwave amplification by stimulated emission of radiation. Predecessor to the laser, the maser or...
thermophotovoltaic
Thermophotovoltaic (TPV) refers to a technology that converts heat energy into electricity using the principles of...
Fourier images
The series of images formed when periodic objects are exposed to collimated monochromatic radiation and that result from...
infrared photoconductor
A photoconductor that demonstrates increased conductivity during its exposure to infrared radiation.
actinochemistry
The study of chemical changes produced by radiation.
emission spectroscopy
A study of the energies and wavelengths of radiation emitted by atoms and molecules when particular physical conditions are...
electron image tube
A cathode-ray tube that increases the brightness or size of an image or forms a visible image from invisible radiation. The...
facet erosion
The degradation of the facets in a laser diode due to the intensity of radiation.
radiation pyrometer
Also known as radiation thermometer. A pyrometer in which the radiant intensity from the source to be measured is used to...
immersed detector
A radiation detector with its active medium mounted within a lens that focuses the radiation signal. The improvement in...
enclosed arc lamp
An arc lamp whose carbon electrodes are enclosed in a transparent chamber, resulting in an arc that is steadier, lasts...
electromagnetic wave
Wave of radiation identified by individual fluctuations of electric and magnetic fields.
collimation
1. The process of aligning the optical axes of optical systems to the reference mechanical axes or surfaces of an...
source
A physical source of radiation, as contrasted to illuminant. See illuminant.
Planck's (radiation) law
The formula describing the spectral radiant emittance of a perfect blackbody as a function of its temperature and the...
wood effect
The phenomenon in which alkali metals are transparent to ultraviolet radiation.
rem
The unit of the dose of any radiation that produces the same biological effect as one roentgen of x-ray.
xenon flashtube
A high-intensity source of incoherent white light in which a capacitor is discharged through a tube of xenon gas; often used...
detector-Dewar assembly
A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments,...
modulation frequency
Rate at which optical radiation or a signal is varied through the use of a mechanical or electronic chopper. Also called...
atomic fluorescence spectroscopy
The analysis of fluorescence emitted by discrete atoms, in flames, that have absorbed radiation from an external source. It...
intrinsic photoconductivity
The absorption of a photon raising an electron across the forbidden gap from valence to conduction band of the semiconductor...
electromagnetic radiation
Radiation emitted from vibrating charged particles. A combination of oscillating electrical and magnetic fields that...
mercury vapor light source
A lamp that has mercury in a tube or bulb that has first been evacuated. The electricity travels through the vapor between...
photoswitch
A solid-state device that acts as a high-speed power switch, and that is activated by incident radiation.
indirect illumination
The light formed by visible radiation that, in traveling from light source to object, undergoes one or more reflections. In...
blackbody source
A blackbody source, often simply referred to as a blackbody, is a theoretical or practical physical object that absorbs all...
radiation thermocouple
A thermocouple that is used in infrared spectroscopy to detect a sample's infrared emittance. See thermocouple.
solarization
1. The reduction in the developable density of a photographic emulsion that has been extremely overexposed. 2. In a laser...
pulsar
An astronomical body that emits radiation concentrated by a strong magnetic field into two beams that rotate, giving a...
spatially coherent radiation
The correlation of radiation between the phases of monochromatic radiation emanating from two separate points.
infrared thermal detector
Used to detect radiation from the infrared region. The functional process includes absorption of infrared radiation, which...
thermal-infrared camera
A thermal-infrared camera, often referred to simply as a thermal camera, is a type of imaging device that detects infrared...
chemical actinometer
A light-sensitive detector having a chemical compound that reacts when exposed to light. It is used in photochemistry and...
reflected ultraviolet photography
A photographic method used to obtain an image of a subject by means of its reflectance of incident ultraviolet radiation. An...
electro-optic detector
A device that detects radiation by utilizing the influence of light in forming an electrical signal. It may be a phototube;...
radioparent
Capable of being penetrated by some form of radiation.
scintillation
1. The variation in intensity of a light beam as it travels through the atmosphere. 2. In radiation physics, a light flash...
photosynthetically active radiation
Photosynthetically active radiation (PAR) is the 400- to 700-nm region (visible light) of the electromagnetic spectrum that...
electrostatic tape camera
A camera that records its images electrostatically on plastic tape; used in situations where radiation would have an adverse...
bremsstrahlung
Electromagnetic radiation that is emitted by an electron as it is accelerated or decelerated while moving through the...
Einstein coefficients
Three proportional coefficients labeled Am, Bmn, and Bnm, that respectively characterize the rate of spontaneous emission,...
photoconductive film
A film of material that exhibits varying conductivity based upon its absorption of varying amounts of photon radiation.
grating monochromator
An optical instrument used to isolate a narrow bandwidth of optical radiation using a diffraction grating as the dispersive...
spectrofluorometer
An automatic scanning instrument that is used to study a substance's fluorescence over a wide range of wavelengths. It...
germicidal UV
Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing...
marcuse loss theory
A theoretical analysis of radiation loss from planar optical waveguides due to scattering by surface irregularities/surface...
excited state
The stationary state of an ion, atom or molecule, above the ground state that is produced by the interaction with the...
infrared lens
An infrared lens is an optical component specifically designed and optimized for transmitting, focusing, or manipulating...
dispersion formula
All formulas that present the index of refraction as a function of a wavelength of electromagnetic radiation. Also called...
enclosed laser device
A laser or laser system positioned within an enclosure to prevent dangerous optical radiation from leaving the enclosure.
cross-linked plastic
Plastic in which the polymer chains become irreversibly joined during molding. The cross-linking can be achieved by heating,...
x-ray streak camera
A diagnostic instrument that uses a photocathode design to see a broad range of x-ray radiation by streaking the...
distance-luminosity relationship
In astronomy, the relation that states that the intensity of a star's visible radiation is inversely proportional to the...
Auger effect
The radiation-free transition that takes place within an ion, in which inner-shell vacancies in neutral atoms are filled by...
optics
Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter...
Bragg method of crystal analysis
A technique in which a beam of x-rays is directed against a crystal, the atoms of which, because of their lattice...
linar
Celestial point sources that emit specific wavelengths of radiation that appear on spectral charts as narrow lines. The term...
surface electromagnetic waves
Waves that propagate along the interface between two different media without radiation with exponentially decaying...
light quantum
The individual coherent series of lightwaves that defines a quantum of radiant energy. Light quantum is equal to hv, h being...
Fresnel diffraction
1. Also known as near-field diffraction. The field of radiation sent through an aperture in an absorbing screen at large...
fluence
Fluence is a term used in various scientific and technical disciplines to describe the amount of something per unit area....
photoionization
The ionization that occurs in gas affected by the action of radiation quanta.
astronomical photography
The use of photographs to record astronomical objects and phenomena for purposes of physical observation and measurement of...
nonionizing radiation
Radiation that does not produce free electrons and ions, or electrically charged particles.
terahertz radiation
Electromagnetic radiation with frequencies between 300 GHz and 10 THz, and existing between regions of the electromagnetic...
ground state
Also known as ground level. The lowest energy level of an atom or atomic system. A material in the ground state is not...
quenching
The inhibition or elimination of one process by another process. The stimulated emission of a laser oscillator can be...
hot mirror
A mirror with a coating that reflects infrared radiation and transmits visible light.
dark noise
The noise produced in a photodetector when the photocathode is shielded from all external optical radiation and operating...
beamwidth
The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The...
thermal radiation
The emission of radiant energy in which the energy emitted originates in the thermal motion of the atoms or molecules of the...
double diffuse density
Measurement derived from calculation when incident flux of a negative is entirely diffuse and all radiation transmissions...
Doppler principle
The theory established by Christian J. Doppler in 1842 that states that the rate of change in distance between a perceiver...
homogeneous multilayer coating
A thin film of absorbing or nonabsorbing layers in which the absorption of radiation at any point is directly proportional...
laser damage
A natural or mechanical system adversely affected by the influence of laser radiation. During laser damage the common effect...
backscatter
Backscatter refers to the phenomenon in which radiation or waves are scattered backward, opposite to the direction of the...
radiation length
The average length in a specific material in which a relativistic charged particle will lose 67 percent of its energy by...
major lobe
With respect to a beam, the radiation lobe having the direction of maximum radiation.
single-defect model
A model that predicts laser-induced damage to thin films caused by irradiation of identical, randomly distributed film...
resonance fluorescence
In atomic fluorescence spectroscopy, fluorescence emitted by an atom at a spectral line of a wavelength identical to that of...
photoconductive detector
A device for detecting visual and infrared radiation using a photoconductor as the principle sensing element.
radiant
Pertaining to electromagnetic radiation, with the contributions at all wavelengths of interest weighted equally.
uviol glass
A type of glass contrived by Schott that is highly transparent to ultraviolet radiation.
blackbody simulator
A source that attempts to create the characteristics of an ideal blackbody. It consists of a cavity, generally spherical,...
radio telescope
An instrument designed to collect naturally formed extraterrestrial electromagnetic radiation within the radio frequency...
deep ultraviolet
Deep ultraviolet (DUV or deep-UV) refers to a specific range of ultraviolet light with shorter wavelengths than those in the...
phosphor
A chemical substance that exhibits fluorescence when excited by ultraviolet radiation, x-rays or an electron beam. The...
negative absorption
Amplification; the result of the excess of stimulated radiation over absorbed radiation.
Ultraviolet-C
Ultraviolet-C (UV-C) refers to a specific range of ultraviolet radiation with shorter wavelengths than those of visible...
long-pass filter
A long-pass filter is an optical filter that allows longer wavelengths of light to pass through while blocking or...
light
Electromagnetic radiation detectable by the eye, ranging in wavelength from about 400 to 750 nm. In photonic applications...
surface-emitting laser diode
A semiconductor laser diode that emits light perpendicular to the active region. The output radiation is taken through the...
spectroscopy
Spectroscopy is a technique used in the study of interactions between matter and electromagnetic radiation. It involves...
optical air mass
A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere...
integration time
Integration time, in the context of optics, imaging systems, and sensor technology, refers to the duration over which a...
absorption peak
An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular...
heliograph
An instrument designed to record the duration and intensity of solar radiation.
spectral luminous efficiency
Ratio of the radiant flux at a particular wavelength lm to that at any other wavelength l, such that both radiations produce...
ultraviolet reflectance
Ultraviolet reflectance refers to the ability of a material or surface to reflect UV light. Ultraviolet light is...
zero-order reflection grating
A grating that specularly reflects the specified long radiation wavelengths and diffracts the shorter wavelengths off in...
continuous spectrum
The radiation spectrum of matter found in condensed states, liquid or solid, that is continuous and not a line spectrum. The...
saturable absorber
A laser dye whose absorption coefficient drops at high levels of incident radiation. The phenomenon is often called...
long-wave infrared
Long-wave infrared (LWIR) refers to a specific range of the infrared spectrum. Infrared radiation is divided into three main...
biophotonics
The technology that deals with the interaction of organic materials with light and other forms of radiant energy whose...
fluorography
The photographic recording of a visible image formed by the impact of invisible radiation on a fluorescent screen.
nuclear magnetic resonance spectroscopy
That branch of spectroscopy that applies to the study of interactions between energy and atomic nuclei. The simultaneous...
Lorentz oscillator model
The Lorentz oscillator model is a theoretical model used in physics to describe the response of a charged particle (such as...
linewidth
1. The range of frequencies or wavelengths over which radiations are absorbed or emitted in a transition between a specific...
radiation angle
Half the vertex angle of the cone of light emitted by a fiber.
nonthermal radiation
The radiation emitted from a group of charged particles that does not depend on the temperature of the source in which those...
ionization gauge
A type of radiation detector that depends on the ionization produced in a gas by the passage of a charged particle through...
silver-disc pyrheliometer
An instrument that uses a blackened silver-disc reflector with a shutter to create temperature fluctuations that are...
infrared vidicon
A vidicon that has a photoconductive surface that can be excited by infrared radiation.
phosphorescence spectroscopy
The spectroscopic study of the radiation emitted by the lifetime of phosphorescence.
ideal polarization rotator
A theoretical instrument conceived of as a box that receives a beam of radiation of any arbitrary polarization angle and...
pyrheliometer
An instrument for measuring the intensity of solar radiation.
color-translating microscope
A type of compound microscope that uses three visible wavelengths to translate details produced by invisible radiation.
luminous
Pertaining to electromagnetic radiation as perceived by the eye; that is, with the contributions as wavelengths in the...
extreme ultraviolet
Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum....
null process
Commonly performed in spectroscopy, the optical null process is a method for radiation detection whereby physical detectors...
solar heat storage
The process of transferring collected energy from solar radiation into a heat-absorbing medium (e.g., an insulated tank of...
Debot effect
The conversion of an internal latent image into a surface latent image through exposure to infrared radiation. The converse...
flux concentration
The intensity of radiation transmitted to a receiver.
radiation pressure
The force exerted on a surface by radiation.
broadband incident radiation
 collimated radiation
Radiation in which every ray from any given object point can be considered to be parallel to every other. This is never...
cadmium lamp
A mercury vapor discharge lamp that has cadmium added to emit radiation in the red region as a complement to the mercury...
cosine collector
Translucent collector developed to compensate for the partial blocking of a flat surface's collection angle that normally...
beam converter
A device used to alter the shape of or energy distribution within a beam of radiation.
frequency
With reference to electromagnetic radiation, the number of crests of waves that pass a fixed point in a given unit of time,...
photronic cell
A photovoltaic cell usually sensitive to infrared radiation. It may have a copper base and a film of cuprous oxide. When it...
lithography
Lithography is a key process used in microfabrication and semiconductor manufacturing to create intricate patterns on the...
filter grating
A grating used as a reflectance filter, particularly in the far-infrared. Small plane gratings, blazed for the wavelength of...
Nichols radiometer
An instrument devised by Nichols and Hull for use in the measurement of radiation pressure. The device has two small...
microbubble resonator
A microbubble resonator is a device used in photonics and optical physics for the precise manipulation of light waves. It...
atmospheric optics
The analysis of the properties of radiation, such as light, when acted upon by variations in the atmosphere. Blue and red...
medical lasers
Medical lasers are devices that produce intense beams of light with specific characteristics and properties, which are used...
solar simulation
The simulation of solar radiation in the infrared and ultraviolet spectrum for the analysis of extraterrestrial sunlight and...
diffuse reflector
A reflecting surface that scatters radiation that is incident on it, thus producing diffuse reflection.
line spectrum
A spectrum formed by radiation whose energy values of the property being measured cluster about at least one discrete value,...
thermal imaging
The process of producing a visible two-dimensional image of a scene that is dependent on differences in thermal or infrared...
cadmium lines
The three lines in the spectrum of cadmium that have the purest radiations and that were first used by Michelson to...
Q-switched pulse
A laser output that occurs when the cavity resonator Q is first kept very low, using rotating mirrors or saturable...
radiation mode
A mode in an optical waveguide whose fields are transversely oscillatory everywhere external to the waveguide. It exists...
threshold test
In laser damage testing, the exposure of many sites of a sample to different intensities of laser irradiation to discover...
photographic thermometry
The photographic recording of the heat radiation emitted from various points on the object as corresponding density...
night-vision device
A device that uses low-level visible radiation or infrared radiation to produce a visual image of a night scene. These...
remote sensing
Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on...
total radiation pyrometer
Also known as a pyrradiometer. An instrument that is designed to measure heat radiation nonselectively; e.g., the...
spectrophotoelectric
Characteristic of the relationship between photoelectric activity and the wavelength of incident radiation.
dark current
The current that flows in a photodetector when there is no optical radiation incident on the detector and operating voltages...
coherent light source
A light source that is capable of producing radiation with waves vibrating in phase. The laser is an example of a coherent...
optoelectronic
Pertaining to a device that responds to optical power, emits or modifies optical radiation, or utilizes optical radiation...
synchrotron
A synchrotron is a type of particle accelerator that uses magnetic fields to steer charged particles, typically electrons or...
scintillation counter
An instrument designed to measure radiation indirectly through the use of several phosphors and a photomultiplier tube. The...
nonlinear optical detector
A type of radiation detector designed to recognize nonlinear optical effects, such as the Raman effect, by means of a...
x-ray analysis
The series of processes used to identify and evaluate crystal structure by using crystalline solids to diffract x-rays. In...
deuterium discharge lamp
A discharge lamp filled with deuterium to produce high-intensity ultraviolet radiation for use in spectroscopic analysis.
short wavelength infrared
Short wavelength infrared (SWIR) refers to the portion of the infrared spectrum that encompasses wavelengths roughly between...
Planck's constant
The universal constant h that has a value of 6.6260693 x 10-34 Js. A quantum of energy is equal to the product of the...
light negative
That property of a substance that determines that there will be a decrease in conductivity when exposed to light radiation.
radio astronomy
The detection and analysis of naturally formed extraterrestrial electromagnetic radiation within the radio frequency range...
fluorescent microscope
A type of optical microscope that allows the specimen being viewed to be irradiated by ultraviolet, violet and occasionally...
spontaneous emission
Radiation emitted when a quantum mechanical system drops spontaneously from an excited level to a lower level. This...
vacuum ultraviolet source
Any source that emits radiation of wavelengths between 100 and 300 nm. Instruments used to study these sources must be...
continuous-wave laser
A laser that emits radiation continuously rather than in short bursts, as in a pulsed laser.
infrared
Infrared (IR) refers to the region of the electromagnetic spectrum with wavelengths longer than those of visible light, but...
Thomson scattering
The scattering of electromagnetic waves by free electrons, whereby the incident radiation and the scattered radiation are of...
electron cyclotron maser
A maser that relies on the fact that electrons in orbital motion in high-magnetic fields will emit energy at the cyclotron...
beam expander
A system of optical components designed to increase the diameter of a radiation beam. Usually an afocal system.
short-wave radiation
Characterizes the significant solar radiation at the surface of the earth, so named because its spectral range extends only...
depletion region
The region at the PN junction in a semiconductor radiation detector where the potential energies of the two materials create...
surface wave
A wave that is guided by the interface between two different media or by a refractive index gradient in the medium. The...
accessible emission
The present radiation level within a laser or electromagnetic radiation operating area.
color conversion filter
A filter that serves to alter the color temperature and the mired value of the radiation emitted by a source.
pumping band
A group of energy levels to which ions in the ground state are initially excited when pumping radiation is applied to a...
radiography
A photographic process using x-ray radiation or the g-rays of radioactive materials.
shutter
A mechanical or electronic device used to control the amount of time that a light-sensitive material is exposed to radiation.
ultraviolet photomicrography
The photographic recording that uses ultraviolet radiation to irradiate the microscope sample being examined and to form an...
atomic absorption spectroscopy
The analysis of the atomic structure of a sample by means of a source radiation that is absorbed and emitted by the sample...
roentgen
An obsolete term once used to describe a unit of radiation dosage.
noncoherent radiation
Radiation having waves that are out of phase in space and/or time.
molecular motor
A molecular motor refers to a nano-sized device composed of organic molecules or other small-scale components that can...
solar plasma
Plasma formed by heat radiation from the sun.
emission of sky
Thermal emission caused by the unity in absorption bands that must be discriminated when calculating radiation intensity of...
Clayden effect
The desensitization of the first photographic exposure after it has been subjected to high-intensity radiation.

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