Photonics Dictionary: H

The broadening of a laser's line width in a way that affects every atom (or molecule), and thus the whole system, in the same manner. Examples are collision broadening, and natural or intrinsic...

That part of the cladding wherein the refractive index is constant within a specified tolerance, as a function of radius.

A thin film of absorbing or nonabsorbing layers in which the absorption of radiation at any point is directly proportional to the electrical field intensity at that point.

The parallel orientation of the molecular axes of the nematic molecules in a nematic crystal, relative to the electrode plates.

A junction between semiconductors that differ in their doping level conductivities but not in their atomic or alloy compositions.

An optical test table made up of two outer layers or "skins'' bonded to either side of a honeycomblike core, usually of aluminum or steel. It results in equal quality with greatly reduced weight...

An infrared device used in satellites and rockets to determine a heat horizon for the Earth at altitudes (above 200 miles) where the visible horizon cannot be discerned. The device scans the infrared...

In television, the period during which the electron beam is cut off while the raster returns from the right-hand side of the screen to the left.

A type of paper chromatography that produces a chromatogram that is horizontal instead of vertical.

A device that controls the output of a television receiver's horizontal oscillator.

In television, the number of individual pixels that can be distinguished in a horizontal scanning line; also called horizontal definition.

Horizontal concentrations that comprise the dominant factor in atmospheric gradient correction. The range bias near due north and due south azimuths coincides with the systematic decrease in surface...

The rotation of an instrument (or the line of sight of an optical system) in a horizontal plane; transverse.

The locus of the points in the field of binocular vision that are observed singly. The images of these points correspond to the respective retinal points.

A method of manufacturing polycrystalline infrared-transmitting optical fiber by heating a single halide crystal billet and forcing it through a die.

Term applied to laser technology to denote an area of above-average intensity often attributable to atmospheric inconsistencies.

The center of a local area network in the star topology.

A glass rhomb that is used in photometry to compare two illuminated surfaces. This is accomplished by the rhomb's angles, which transmit two light beams, one from each of the two surfaces, so that...

The perceptual term for that aspect of color described by words such as red, yellow or blue. Achromatic colors, such as white, gray and black, do not exhibit hue.

A visual spectrophotometer with a rhomb located directly before the entrance aperture of a constant-deviation spectrophotometer.

A plotted relation between Log E (logarithm to base 10 of exposure in metercandle seconds) and density (logarithm to base 10 of opacity).

An ocular having two planoconvex lenses that are formed from similar glass and that are separated by a space equal to half the sum of their focal lengths. This eyepiece is free of lateral chromatic...

An analysis used for problems of wave propagation. The principle notes that each point of an advancing wavefront is the center of a new disturbance, the source of a new series of waves. It also notes...

A cable assembly containing both optical fibers and copper electrical conductors in the same jacket.

Any integrated circuit that also makes use of one or more discrete components; frequently used to describe circuits that combine both photonic and electronic components.

A cryogenic cooler device that is an intermittent Joule-Thomson refrigerator with a passive radiator serving as the precooler. Used for satellite applications, the device has Joule-Thomson and gas...

A wave in the electromagnetic spectrum that has both electrical and magnetic field vectors in the direction of propagation.

A device where each pixel in the detector array is mated with a preamplifier on a single silicon chip, providing sensing and signal processing capabilities.

A single housing that includes means of recording an image photographically and electronically.

A mode possessing components of both electrical and magnetic field vectors in the direction of propagation.

A sensor module used in advanced pattern recognition systems, containing signal-processing integrated circuits stacked and connected by a busing circuit.

Device in which the various circuit elements are fabricated in different substrate materials and then appropriately joined together so that the various substrate materials can be chosen to optimize...

A hydrogel is a three-dimensional network of polymer chains that are hydrophilic, meaning they have a strong affinity for water. This network structure allows hydrogels to absorb and retain large...

A gas laser having a mixture of gases that makes it useful in the lab. The mixture of gases flows through a pressure and gas-flow-rate-regulated, sealed vessel with such a gain that only the...