Photonics Dictionary: H

An electron tube whose electrical characteristics will not be affected by gaseous ionization because of its high degree of evacuation. Also known as a hard tube.

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

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.

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...

With respect to waveguides, the continuous change in the direction of the axis of the wavelength, during which the axis is perpendicular to the direction of polarization.

The term half bandwidth (HBW) generally refers to the width of a spectral band or frequency range at half of its maximum amplitude. It is commonly used in the context of signal processing, optics,...

A semicircular, half-wave quartz plate between the polarizer and analyzer. It often is used in forming precision settings with a polariscope.

In chemistry, a halide refers to a chemical compound containing one or more halogen atoms bonded to another element. The halogens are a group of elements in the periodic table that includes fluorine...

The development of a transverse electric field in a solid material when it carries an electric current and is placed in a magnetic field that is perpendicular to the current.

A halogen lamp, also known as a tungsten halogen, quartz-halogen, or quartz iodine lamp, is an incandescent lamp that uses a tungsten filament surrounded by a small amount of halogen gas, such as...

A type of optical fiber in which a silica core is surrounded by a hard polymer or similar material much stronger than the customary cladding material.

Harmonic generation refers to a nonlinear optical process in which incoming photons interact with a material and produce new photons at integer multiples of the frequency of the incoming photons....

An instrument designed to calculate the amplitude and phase of the different harmonic elements of a radiation wave utilizing a graph of the wave.

A test for spherical aberration, coma or astigmatism in which incident rays from a point source are isolated by small holes in a metal disc located close to the lens or mirror under test....

A calorimetric calculation from which the temperature vs. time dependence of any point on a sample can be determined, provided surface and bulk absorption, thermal conductivity and heat transfer...

A series of flanges or other conducting surfaces, usually metal, attached to an electronic device to transmit and dissipate heat that might damage internal circuitry.

A small mass spectrometer used to find leaks in a vacuum system by detecting the presence of helium. Using a magnetic deflection device that is permanently tuned to helium, it is capable of detecting...

Laser cavity bounded by a plane mirror and a concave spherical mirror with the plane mirror located at the center of curvature of the concave mirror.

The inductance of a closed circuit in which an electromotive force of one volt is produced when the electric current in the circuit is varied uniformly at a rate of one ampere per second.

Laboratory experiments that focus on demonstrating new capabilities of a certain technology or device, usually without consideration of industrial or commercial practicality.

In optical communications, the translation of optical signals into radio signals, lowering their frequency in detection from greater than 1014 Hz to less than 1010 Hz, so that further signal...

The combination of more than one type of small-molecule monomer into a polymer.

High dynamic range (HDR) refers to a technology that allows for a broader and more dynamic range of luminosity in visual content, such as images or videos. It is particularly associated with displays...

High harmonic generation (HHG) refers to a nonlinear optical process in which intense laser light interacts with a gaseous medium, typically an atom or a molecule, to produce harmonics of the...

A filter possessing one transmission band that extends from a cutoff frequency other than zero to frequency at infinity.

A cloud chamber designed to maintain the gas within it at a high pressure as a means of reducing the range of the high-energy particles and, subsequently, increasing the chances of observing...

A high-speed motion camera, also known as a high-speed camera or slow-motion camera, is a specialized imaging device designed to capture fast-moving events or phenomena at extremely high frame rates....

A camera designed to record at rates exceeding 50 fps. For frame rates up to about 500 fps, an ordinary pull-down mechanism can be used. From 500 to 1000 fps, the film must be moved continuously, the...

Photography involving the recording of events that occur too fast to be perceived by the human eye or recorded by conventional photographic techniques. See high-speed movie camera; high-speed...

Histochemical staining is a laboratory technique used in biology and medicine to visualize specific chemical components within biological tissues. This technique involves the application of various...

A graphic representation of a distribution function such as frequency by means of rectangles whose widths represent the intervals into which the observed values' range is divided and whose heights...

Histology is the branch of biology and medicine that involves the study of the microscopic structure of tissues and organs at the cellular and subcellular levels. It is a field that focuses on the...

A soft, malleable, stable rare-earth element. Holmium laser systems are used in surgical procedures involving the cutting and vaporizing of soft tissue, cartilage and calcific structures.

Holmium lasers are a type of medical laser that utilizes holmium-doped crystals as the gain medium. The term holmium laser is often associated with a specific type of laser used in urology for...

A holographic camera, also known as a holographic imaging system or holographic recorder, is a specialized device used to capture 3D holographic images of objects or scenes. Unlike conventional...

A holographic grating is a type of diffraction grating that is produced using holographic recording techniques. It consists of a periodic structure of alternating transparent and opaque regions,...

The holographic recording of a microscopic specimen whereby magnification is achieved by alteration in a wavelength or radius of curvature between recording and reconstruction of the wavefront. With...

Holographic tomography is an advanced imaging technique that combines holography and tomography to provide three-dimensional reconstructions of transparent or weakly scattering objects with high...

Holography is a technique used to capture and reconstruct three-dimensional images using the principles of interference and diffraction of light. Unlike conventional photography, which records only...

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

A system of sensors and related instrumentation that allows a navigable object (usually a missile) to locate its destination by some distinguishing characteristics of that target, and then calculate...

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...

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

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.

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.

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...

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