Photonics Dictionary

An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

The layer of material in a laser diode from which the optical radiation is emitted; light producing region

An angstrom, symbolized by the Ångström or Å, is a unit of length used to express atomic and molecular dimensions. It is equal to 0.1 nanometers or 1 × 10-10 meters. The...

A waveguide that has a core with a lower refractive index than the refractive index of the cladding. This structure can limit the power of the transmitted beam by removing unwanted radiation, for...

An arc flash is a sudden release of electrical energy due to an electric arc — a continuous, high-current discharge of electricity between conductors or from a conductor to ground. Arc flashes...

In present usage, especially for spectroscopic identification, an arc between electrodes that serves as a radiation source. Gas tubes that contain mercury vapor and mixtures of helium, neon and argon...

The analysis of the properties of radiation, such as light, when acted upon by variations in the atmosphere. Blue and red skies, along with ice halos, glories, coronas and rainbows can all be...

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

Attosecond-pump attosecond-probe spectroscopy (APAP) is an advanced technique in ultrafast spectroscopy that allows scientists to study the dynamics of electronic processes occurring on extremely...

The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The beamwidth is a measure of the rate of divergence or convergence of a light...

The technology that deals with the interaction of organic materials with light and other forms of radiant energy whose quantum unit is the photon. This includes the emission, detection, absorption,...

Radiation from the invisible (usually ultraviolet) region of the spectrum.

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...

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.

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.

The radiation produced when a charged particle traverses a medium that has a refractive index considerably greater than unity. The moving particle has a velocity that exceeds the velocity of light in...

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.

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

Radiation in which every ray from any given object point can be considered to be parallel to every other. This is never completely the case: The light from a star is really diverging, and all...

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.

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...

Light produced by visible radiation that moves from the light source to the object without reflection. With respect to microscopy, this is the light that directly strikes the stage of the microscope...

Directed energy refers to a type of energy that is emitted and transferred in a controlled direction. The term is often associated with military and technological applications where energy, typically...

A device that detects radiation by utilizing the influence of light in forming an electrical signal. It may be a phototube; a photoconductive, photovoltaic or photojunction cell; a phototransistor;...

Radiation emitted from vibrating charged particles. A combination of oscillating electrical and magnetic fields that propagates through otherwise empty space with the velocity of light. This constant...

A cathode-ray tube that increases the brightness or size of an image or forms a visible image from invisible radiation. The focal plane for the optical image is a large, light-sensitive, cold...

Epitaxial equipment refers to a set of specialized tools and systems used in the process of epitaxy, which is the growth of crystalline layers on a substrate material. Epitaxial growth is a critical...

An Er:YAG laser is a type of solid-state laser that uses a crystal made of erbium-doped yttrium aluminum garnet (Er:Y3Al5O12) as the gain medium. The erbium (Er) ions are introduced into the crystal...

Extreme ultraviolet (EUV) refers to a specific range of electromagnetic radiation in the ultraviolet part of the spectrum. EUV radiation has wavelengths between 10 and 124 nanometers, which...

The effect discovered by Faraday in 1845 whereby nonoptically active materials or substances become capable of rotating the polarization plane of polarized radiation (light) passed through them when...

A fiber-coupled photoconductive antenna (FCPA) is a type of optoelectronic device that combines a photoconductive antenna with optical fibers for the purpose of generating or detecting terahertz...

Fluence is a term used in various scientific and technical disciplines to describe the amount of something per unit area. The specific meaning of fluence can vary depending on the context in which it...

Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Specifically, fluorescence involves the absorption of...

A fluorescent screen refers to a phosphorescent or fluorescent-coated surface that emits visible light when exposed to other forms of electromagnetic radiation, such as x-rays or ultraviolet light....

A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a beam of accelerated electrons as the lasing medium. Unlike traditional...

With reference to electromagnetic radiation, the number of crests of waves that pass a fixed point in a given unit of time, in light or other wave motion. Expressed in hertz or cycles per second.

FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based...

Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing or inactivating microorganisms, including bacteria, viruses, and fungi. The...

A thermal radiation detector consisting of a small cell with a blackened plastic front face that bulges slightly when heat is received by it. The bulging tilts a small mirror, which, in turn, varies...

A framework or latticework having an even arrangement of rods, or any other long narrow objects with interstices between them, used to disperse light or other radiation by interference between wave...

Transparencies that represent progressive steps in the amount of transmitted radiation for administering predetermined amounts of radiation to a radiation-sensitive substance. The steps are...

The light flash that occurs when an electrical field is applied to a phosphor already excited by ultraviolet radiation.

Radiation consisting of more than a single wavelength in the visible region of the spectrum.

A mirror with a coating that reflects infrared radiation and transmits visible light.

Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a hyperspectral imaging system. In hyperspectral imaging, the electromagnetic spectrum is...

An image intensifier, also known as an image intensification tube or image intensification device, is a specialized electronic device used to amplify low-light-level images to make them visible to...

The emission of light by thermal radiation of a temperature high enough to render the source of radiation visible.