Photonics Dictionary

An enclosure whose walls are coated to absorb completely all radiation striking them.

An ideal body that completely absorbs all radiant energy striking it and, therefore, appears perfectly black at all wavelengths. The radiation emitted by such a body when heated is referred to as...

A source that attempts to create the characteristics of an ideal blackbody. It consists of a cavity, generally spherical, made of an opaque material and insulated from thermal effects, with a small...

A blackbody source, often simply referred to as a blackbody, is a theoretical or practical physical object that absorbs all electromagnetic radiation incident upon it and emits radiation in a...

The law given by the formula: that is, the frequency of radiation emitted or absorbed by a system when E2 and E1 are the energies of the states among which transition takes place, and h is...

A thermometric instrument used for the detection and measurement of radiant energy. Its essential component is a short narrow strip covered with a dead black absorbing coating and mounted at the...

A technique in which a beam of x-rays is directed against a crystal, the atoms of which, because of their lattice arrangement, reflect the ray in the same way as a series of plane surfaces. If the...

Electromagnetic radiation that is emitted by an electron as it is accelerated or decelerated while moving through the electric field of an ion.

Brillouin scattering is a phenomenon in physics where an incident electromagnetic wave (usually light) interacts with acoustic phonons (quantized lattice vibrations) in a material, resulting in the...

A device that functions throughout the continuous radiation of a linearly polarized plane wave, and whose nonreciprocity arises from the Faraday rotation of linearly polarized radiation.

A mercury vapor discharge lamp that has cadmium added to emit radiation in the red region as a complement to the mercury vapor's blue and green radiation.

The three lines in the spectrum of cadmium that have the purest radiations and that were first used by Michelson to calculate the standard meter.

The narrowest line of the cadmium spectrum; the red line has the purest radiation.

The production of visible light by infrared radiation whereby the light is produced by heat and not by any direct change in wavelength; the transformation is indirect.

Name originally given to the sun's infrared radiation by Sir William Herschel in his Philosophical Transactions of 1800.

Light produced when a metal is bombarded with high-velocity electrons causing small amounts of the metal to vaporize and emit radiation. Also known as electronoluminescence.

In an interferogram, an intense portion of the recording that corresponds in size to the amount of infrared radiation incident on the detector.

An instrument that detects high-energy charged particles by analysis of the Cerenkov radiation that they emit.

A photoelectric detector consisting of a glass tube internally coated with a low conductance material. Voltage applied along the tube causes photoemission from the photocathode at the end of the tube...

A light-sensitive detector having a chemical compound that reacts when exposed to light. It is used in photochemistry and relies on the chemical reaction to determine the amount of incident radiation.

Scanning characterized by the generation of a plane or right circular cone with a vertex angle of about 180° by the direction of maximum radiation.

The desensitization of the first photographic exposure after it has been subjected to high-intensity radiation.

Glass that transmits near-ultraviolet radiation but is opaque in the visible region. Also known as woods glass.

A reticle carrying patterns of various forms that can be rotated in an optical beam to cause variations in the intensity of the beam. It also is used in infrared detectors to scan the object field...

A light source that is capable of producing radiation with waves vibrating in phase. The laser is an example of a coherent light source.

A cathode that emits electrons, not with the influence of heat radiation, but by means of a high-voltage gradient at its surface.

A mirror whose coating serves to reflect visible radiation while transmitting the infrared.

1. The process of aligning the optical axes of optical systems to the reference mechanical axes or surfaces of an instrument. 2. The adjustment of two or more optical axes with respect to each other....

A filter that serves to alter the color temperature and the mired value of the radiation emitted by a source.

A type of compound microscope that uses three visible wavelengths to translate details produced by invisible radiation.

The phenomenon observed by A.H. Compton in 1923 -- that some scattered radiation possesses a longer wavelength and correspondingly smaller frequency than the incident radiation. It may be described...

The radiation spectrum of matter found in condensed states, liquid or solid, that is continuous and not a line spectrum. The details of this spectrum are almost independent of the matter emitting the...

A laser that emits radiation continuously rather than in short bursts, as in a pulsed laser.

Translucent collector developed to compensate for the partial blocking of a flat surface's collection angle that normally occurs in spectroradiometry. The device samples radiant flux according to the...

A technique used in integrated optics where a groove is cut on a substrate surface and covered by a thin film to facilitate the construction of filters, resonators, beamsplitters and grating couplers...

Plastic in which the polymer chains become irreversibly joined during molding. The cross-linking can be achieved by heating, chemical agents or irradiation.

The use of chemicals or radiation to induce a desired change in a substance; e.g., some optical adhesives are set by exposure to ultraviolet light and are said to be UV-curing.

The current that flows in a photodetector when there is no optical radiation incident on the detector and operating voltages are applied.

The noise produced in a photodetector when the photocathode is shielded from all external optical radiation and operating voltages are applied.

The conversion of an internal latent image into a surface latent image through exposure to infrared radiation. The converse of the Herschel effect.

Deep ultraviolet (DUV or deep-UV) refers to a specific range of ultraviolet light with shorter wavelengths than those in the UV-A and UV-B regions. The exact wavelength range considered as DUV can...