Photonics Dictionary

A nonradiative transition refers to a process in which an electron or an atom undergoes a change in its energy state without emitting a photon. In contrast to radiative transitions, where a photon is...

Also referred to as a band-stop or band rejection filter; a notch filter is a filter that is designed to screen out a very narrow band of radiation by transmitting most wavelengths with little...

A measure of the optical path length for light traveling from the sun or other celestial source through Earth's atmosphere to sea-level relative to the optical path length traveled by light from the...

Optics is the branch of physics that studies the behavior and properties of light, including its interactions with matter and its manifestation as both particle and wave phenomena. It encompasses the...

The improper exposure of a radiation-sensitive medium that results when there is too much radiation exposing the medium, or when the exposure time is too long. The resulting image, in negative form,...

A chemical substance that exhibits fluorescence when excited by ultraviolet radiation, x-rays or an electron beam. The amount of visible light is proportional to the amount of excitation energy. If...

The term photochemical pertains to chemical processes or reactions that are initiated or influenced by the absorption of light. Photochemical reactions involve the interaction of light, often in the...

A chemical compound that exhibits a reversible change in its absorption spectrum upon irradiation with given wavelengths of light.

Photochromic refers to a property exhibited by certain materials, typically organic compounds or dyes, which undergo reversible changes in color when exposed to light. Specifically, photochromic...

The reversible change in the absorption spectrum of certain compounds upon irradiation with a given wavelength of light.

A photomultiplier tube (PMT) is a highly sensitive vacuum tube that detects and amplifies low levels of light. It is widely used in various applications where high sensitivity, fast response times,...

A photonic cavity, also known as an optical cavity, is a structure that confines electromagnetic radiation within a certain region or volume. It is typically composed of materials with different...

A process in which a mixture of one or more monomers, plus a catalyst, polymerize under exposure to light radiation. Photopolymerization permits a hologram to be exposed, fixed and reconstructed in...

A substance that increases a material's sensitivity to electromagnetic irradiation. In photodynamic therapy, a drug used to render a target tissue sensitive to laser light.

Photosynthetically active radiation (PAR) is the 400- to 700-nm region (visible light) of the electromagnetic spectrum that is absorbed and used by the plant for photosynthesis. Also referred to as...

Phototherapy is a medical treatment that involves the use of light to treat various conditions, particularly those related to the skin or mood disorders. There are different types of phototherapies,...

Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically,...

1. With respect to angular subtense, a source of light, such as a star, that is very small. In a lab, a point source may be simulated by imaging a large source onto and through a pinhole, or by...

A lamp with a quartz envelope that transmits radiation generally rich in the ultraviolet.

The energy passed on as electromagnetic radiation; e.g., radio, heat or light waves.

Half the vertex angle of the cone of light emitted by a fiber.

The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of radiation. It implies the capability of bouncing back or redirecting...

Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on Earth's surface is gathered from a distance, typically using sensors onboard...

The fluorescent emission spectrum emitted by certain substances following the irradiation of one of these substances with light that is of the same wavelengths as its fluorescence.

1. The variation in intensity of a light beam as it travels through the atmosphere. 2. In radiation physics, a light flash formed by an ionizing event in a phosphor; a flash formed when rapidly...

An instrument designed to measure radiation indirectly through the use of several phosphors and a photomultiplier tube. The absorption of radiation by any phosphors results in light flashes that may...

A scintillation crystal, also known simply as a scintillator, is a material that emits light when it interacts with ionizing radiation such as gamma rays, x-rays, or charged particles. The emitted...

A scintillation detector is a radiation detection device that utilizes scintillation crystals to detect and measure ionizing radiation, such as gamma rays, x-rays, or charged particles. It consists...

Short wavelength infrared (SWIR) refers to the portion of the infrared spectrum that encompasses wavelengths roughly between 1,000 and 3,000 nanometers (nm). In the electromagnetic spectrum, infrared...

A mechanical or electronic device used to control the amount of time that a light-sensitive material is exposed to radiation.

An aperture, usually rectangular in shape, with a large length-to-width ratio, and a fixed or adjustable shape through which radiation enters or leaves an instrument. The aperture is generally small...

The simulation of solar radiation in the infrared and ultraviolet spectrum for the analysis of extraterrestrial sunlight and its effects on spacecraft, materials and components.

A spectroradiometer is a device used to measure the intensity of light at different wavelengths across the electromagnetic spectrum. It provides a detailed spectral distribution of light, breaking...

Spectroscopy is a technique used in the study of interactions between matter and electromagnetic radiation. It involves measuring and analyzing how different materials absorb, emit, or scatter light,...

A lamp that yields a nonluminous flame; used in the spectroscopic analysis of radiation emitted by a substance placed in the flame.

Also known as Fresnel reflection. That portion of the incident radiation that is reflected from the surface of a refractive material. It is a function of the refractive index of the material. At...

A semiconductor laser diode that emits light perpendicular to the active region. The output radiation is taken through the surface as opposed to through a cleaved mirror.

A synchrotron is a type of particle accelerator that uses magnetic fields to steer charged particles, typically electrons or positrons, in a closed, circular or elliptical path. The name synchrotron...

Radiation emitted by electrons when they travel in circular orbits at speeds close to that of light. Synchrotron radiation occurs in the x-ray and ultraviolet regions of the spectrum. Once considered...

A thermal-infrared camera, often referred to simply as a thermal camera, is a type of imaging device that detects infrared radiation emitted by objects due to their temperature. Unlike traditional...

Thomson scattering is a phenomenon in physics where electromagnetic radiation, such as light, is scattered by charged particles. It is named after the British physicist J.J. Thomson, who first...

Ultraviolet-C (UV-C) refers to a specific range of ultraviolet radiation with shorter wavelengths than those of visible light. UV-C radiation spans the electromagnetic spectrum with wavelengths...