Photonics Dictionary: H

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 gas lamp used in the early 1900s as a physical standard for measurement of luminous intensity. The Hefner unit was superseded by the candle and then by the candela.

A method used in facsimile scanning that sweeps the elemental area across the copy in a spiral motion as the result of the movement of a single turn helix against a stationary bar.

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...

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...

Also known as HCS, an analytical method designed to collect statistically relevant amounts of quantitative data on many parallel cell populations or processes within cells through the combination of...

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...

The dip or gap in the profile of a laser beam's line width when it is both homogeneously and inhomogeneously broadened. When an inhomogeneously broadened spectral line is saturated by incident light,...

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...

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 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...

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.

Also known as constant angle or constant deviation fringes. The interference fringes observed with dense flat plates near normal incidence. The fringes of the Fabry-Perot interferometer are Haidinger...

1. In a cathode-ray tube, the glow surrounding a bright spot that appears on the fluorescent screen as the result of the screen's light being reflected by the front and rear surfaces of the tube's...

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 communications system that can transmit in only a single direction at a time. See duplex.

A plate containing a uniform pattern of transparent holes in an opaque background, the clear area being nearly equal to the opaque area. Used in the printing process.

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...

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 device small enough to be held in a hand that uses a magnifying lens and a translucent back to permit the viewing of photographic transparencies.

Text or images printed on paper or another tangible medium, as opposed to those viewed electronically on a cathode-ray-tube screen.

An optical system that superimposes a synthetic display providing navigational or weapon-aiming information on a pilot's or driver's field of view. The system includes a cathode-ray tube, collimating...

The heat-affected zone (HAZ) refers to the portion of a material, typically metal, that experiences changes in its microstructure and mechanical properties due to the heat generated during welding,...

A heat sink for a laser is a device designed to absorb and dissipate the excess heat generated by the laser during operation. This is crucial to maintain the laser's performance, prevent overheating,...

The process of subjecting glass to temperature cycling to produce physico-chemical reactions that alter its properties. Similar processes can be accomplished with a laser -- most commonly a CO2,...

In the SI system, prefix meaning one hundred, 102.

A helium-neon (HeNe) laser is a type of gas laser that emits visible red light at a wavelength of 632.8 nm. It operates based on the principle of stimulated emission of photons from excited helium...

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.

The ionization and spark emission due to exposure to ultraviolet radiation.

A unit of frequency equivalent to one cycle per second.

A heterojunction is a junction formed between two different semiconductor materials with differing band gaps. These materials can be of the same or different types (e.g., both n-type, both p-type, or...

The Higgs boson is a fundamental particle associated with the Higgs field, a field that permeates the universe and is responsible for giving mass to other fundamental particles through the mechanism...

In plano work, that property of a surface determining that it is convex and contacts a flat test glass at its center.

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...

Optical fiber in which the attenuation exceeds the normally acceptable level for long-haul or data communications use.

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

A very high bandwidth communication line often used in fiber optics.

A high-sensitivity camera is a type of camera designed to perform well in low light conditions, capturing clear and detailed images with minimal noise. These cameras typically feature advanced sensor...

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...

A shutter actuated by means other than mechanical springs for timings on the order of nanoseconds. The shutter is used in the photography of rapid moving objects or events.

A still camera with a shutter capable of opening for a time as short as a fraction of a microsecond. An electronically operated Kerr cell often is employed.