Photonics Dictionary

The investigation of microstructures by an instrument that generates a narrow, highly collimated beam of x-rays.

3D printing, also known as additive manufacturing (AM), is a manufacturing process that builds three-dimensional objects layer by layer from a digital model. This technology allows the creation of...

The absolute luminance threshold is the lowest luminance level of a light source or illuminated object that can be detected by the human eye under specific conditions. This threshold represents the...

In the context of a laser diode, the active region is a critical part of the device where the primary light generation occurs. Laser diode active region: The active region in a laser diode is...

An active-matrix display is a type of flat-panel display technology where each pixel is actively controlled by one or more thin-film transistors (TFTs). This technology is commonly used in liquid...

An old name for the rotating arm moving about an axis of rotation over a divided circle used to measure angles. Now the term refers to a small stadia telescope mounted over a ruler for use in...

The American Astronomical Society (AAS) is a prominent professional association of astronomers and other scientists dedicated to the study of astronomy and related fields. Founded in 1899, the AAS...

Analog-to-digital (A/D) is a process that converts continuous analog signals into discrete digital signals. This process coverts analog signals continuously, which vary smoothly over time, into a...

An aptamer is a short, single-stranded DNA or RNA molecule that can bind to a specific target molecule with high affinity and specificity. Aptamers are often referred to as chemical antibodies due to...

An argon-fluoride (ArF) excimer laser is a type of ultraviolet laser that operates using a mixture of argon and fluorine gases. Excimer lasers are a class of gas lasers that emit light in the UV...

An aspheric mirror is an optical mirror surface that deviates from the shape of a perfect sphere, having a non-spherical surface profile. Unlike traditional spherical mirrors, which have a curved...

An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial objects for observation and analysis. It typically consists of two main optical...

An attoampere (aA) is a unit of electric current in the International System of Units (SI). It is equal to one quintillionth (10-18) of an ampere. The ampere, symbolized as "A," is the base unit of...

An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a...

Back-side illumination (BSI) is a technology used in imaging sensors, particularly in digital cameras, where the light is allowed to enter the sensor from the back side, opposite to where the...

A ball lens is a small, spherical optical component typically made of glass or other transparent materials. It is characterized by its spherical shape, with both its front and back surfaces forming...

In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed. It represents the energy difference between the valence band, which is the...

The smallest amount of photon energy to pass a detector window and be counted.

A beam shaper is an optical device or system designed to modify the spatial profile or intensity distribution of a laser or light beam. The goal is to transform the incoming beam into a desired shape...

A small convergent lens, located between the objective and eyepiece of a microscope, that focuses an image of the upper focal plane of the objective in the focal plane of the eyepiece. It is commonly...

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...

An optical system that rapidly alternates two similar pictures or scenes to permit the detection of small dissimilarities between them.

A blur circle refers to the out-of-focus region in an image captured by an optical system. When an object in a scene is not in perfect focus, its image is spread out into a circular shape on the...

A device for the internal inspection of hard-to-get-at mechanical parts, such as rifle barrels, sewer pipes, oil wells, or gas mains. The long narrow tube used contains a telescope system with as...

A breakout cable, also known as a fan-out cable or breakout assembly, is a type of cable that combines multiple individual cables into a single, larger cable. The breakout cable is designed to...

The fringes used in the Jamin interferometer and produced by light that has been internally and externally reflected by two plane-parallel plates, inclined toward each other at a small angle.

An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...

Brillouin microscopy is a non-invasive imaging technique that utilizes Brillouin scattering to measure the mechanical properties of materials at the microscale. This advanced optical technique...

A microscope that allows examination of a small crystal and conveniently provides linearly polarized object and reference beams so that, by suitable orientation of an anisotropic crystal, the optical...

A calcium indicator is a molecule that is sensitive to changes in calcium ion (Ca2+) concentrations in biological systems. These indicators are commonly used in various fields, including cell...

The use of the photographic process to produce precision copies of an original image that are many times smaller in size. One of its many applications is in microcircuitry.

Carbon fullerenes are a class of carbon-based molecules composed entirely of carbon atoms arranged in a hollow, closed, cage-like structure. The most well-known fullerenes are spherical and are often...

Carrier injection refers to the process of introducing charge carriers (either electrons or holes) into a semiconductor material. Semiconductors are materials with electrical conductivity between...

The Casimir force is a quantum phenomenon that results in an attractive force between two closely spaced uncharged conductive surfaces. This force arises from the quantum vacuum fluctuations of the...

A two-mirror lens design used in astronomical telescopes, the primary being a parabola, the secondary a smaller hyperbola. The image formed is free of spherical aberration and color and is located...

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 a reflecting telescope, the obstruction of the primary mirror by a secondary mirror which blocks a small amount of the light reflected by the primary mirror and introduces additional diffraction.

A small fiber optic endoscope used in laser surgery.

Best point of focus for an image in a beam of light at the smallest cross section of the beam.

Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric) molecules, particularly biomolecules like proteins, nucleic acids, and certain...

An instrument for measuring the vertical angle of an object. It usually contains an accurately made protractor, a sensitive level bubble, and a sighting device, such as a small telescope.

An imaging process in which the single opening of a simple pinhole camera is replaced with many openings called, collectively, the aperture. The recorded picture, which consists of many overlapping...

A compound prism consisting of an assembly of small prisms cemented together that is used in a coincidence rangefinder to transmit the images from the two objectives to a single eyepiece for viewing.

A colloid is a mixture in which one substance of microscopically dispersed insoluble particles is suspended throughout another substance. The particles in a colloid are larger than those in a...

Colloidal quantum dots (CQDs) are nanometer-sized semiconductor particles that are dispersed in a colloidal solution. These quantum dots have unique optical and electronic properties due to their...

A lens aberration, resulting from different magnifications in the various lens zones, that occurs in that part of the image field that is some distance from the principal axis of the system....

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...