Photonics Dictionary

Agents used for testing light sources and natural daylight with visual and instrumental assessment using a set of white metameric pairs.

The analysis and measurement of the fluorescence emitted by a source. Fluorometric processes are more sensitive than light absorption methods and are rapidly being applied in medical and biological...

A fluorophore is a molecule or a portion of a molecule that has the ability to emit light upon excitation by an external energy source, such as ultraviolet or visible light. The process by which a...

The moving spot of light emitted by a source, generally a cathode-ray tube, to illuminate specific points of an area carrying light and dark regions according to a specific pattern.

A microscope that uses a flying spot scanner, directed through the eyepiece, as a light source to determine the features of a transparent specimen. The flying spot is modulated by the varying density...

An incandescent or carbon arc lamp designed with a stable and compact arc or filament that permits it to be used as a light source to be focused by a lens system.

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...

A frequency comb is a precise and regular series of equally spaced spectral lines, or frequencies, that are generated with great accuracy. The term "frequency comb" is often associated with the Nobel...

Two plane mirrors that are not wholly located in the same plane. When light from a point source or slit reflects from the two mirrors, interference bands are revealed in the region where the light...

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...

Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin concentration in the brain. It utilizes near-infrared light to penetrate the...

Fusion ignition refers to the point in a controlled nuclear fusion reaction where the energy released by the fusion reactions becomes self-sustaining, leading to a continuous release of energy...

A GaAlAs laser is a type of semiconductor laser diode that emits light in the near-infrared region of the electromagnetic spectrum. It is composed of layers of gallium, aluminum, and arsenic, hence...

A galvanometric scanner, also known as a galvanometer scanner or galvo scanner, is a type of optical scanning device used to rapidly and precisely direct a laser beam or other light source to...

A system of mirrors that can be used to direct light from a single laser source into any one of a number of separate optical fibers.

Gallium nitride-based light-emitting diodes (GaN-based LEDs) are semiconductor devices that emit light when an electric current passes through them. These LEDs are constructed using gallium nitride...

The global ecosystem dynamics investigation (GEDI) lidar is a state-of-the-art spaceborne instrument designed to study Earth's forests and ecosystems in three dimensions. Developed by NASA, GEDI is...

A field of physics that deals with light as if it truly were composed of rays diverging in various directions from the source and abruptly bent by refraction or turned by reflection into paths...

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 light source made up of silicon carbide or carborundum. It is resistant to the negative temperature coefficient and mechanical distortion.

A neutral-colored gelatin wedge, cast between glass plates, that is used as an intensity scale in certain types of sensitometers; the greater the thickness of the wedge through which light emitted by...

The effect of a powerful gravitational field on light traveling through the field. This effect is detectable in astronomical observations when light from a distant source passes a massive object...

1. The faintly hued ring that is seen to surround a light source viewed through fog or light clouds. The size of scattering particles determines the size of the ring. 2. The ring surrounding a...

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....

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...

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 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,...

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...

A series of permanent holograms in dichromated gelatin formed by opening total page-composer apertures and setting a point source of light in each storage location. It performs much like a...

Homogeneous light refers to light that is uniform in intensity and color across a given area or space. In other words, homogeneous light sources produce illumination that is consistent and evenly...

Metamerism that occurs when the light source is changed.

In optics, an image is the reconstruction of light rays from a source or object when light from that source or object is passed through a system of optics and onto an image forming plane. Light rays...

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...

A hologram in which the image of an object, or the object itself, is located near the hologram recording plane, for optimum image reconstruction. Because the images are close to the hologram plane,...

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

The light formed by visible radiation that, in traveling from light source to object, undergoes one or more reflections. In microscopy, it is the light that falls on the object at right angles to the...

Indirect time-of-flight (iTOF) is a method used in 3D imaging and depth sensing to measure the distance to an object based on the time delay between the emission of a light pulse and the detection of...

Inertial fusion energy (IFE) refers to a proposed method of generating electricity by harnessing the energy released from the fusion of light atomic nuclei, typically isotopes of hydrogen, through a...

Photographic recording that uses infrared radiation as the light source to form an image of a microscopic object and a system of lenses and objectives that are transparent to the radiation. The image...

An infrared source combined with reflecting projection optics to illuminate a target making it visible when observed through an infrared viewing device.

A semiconductor diode operating in either a coherent or incoherent mode that is used as a near-infrared or visible source in triggering light-activated devices.

Also known as integrated exposure. A measurement of light from sources that vary rapidly with time, defined as the integral of instantaneous power and time and expressed as units per second.

Integration time, in the context of optics, imaging systems, and sensor technology, refers to the duration over which a sensor collects and accumulates incoming light or signal. It is a crucial...

The spectrum produced by the interference of light provided that the source used to create the interference has a broad enough emittance to form a spectrum.

An interferometer is a scientific instrument that utilizes the principle of interference to measure differences in the path length, wavelength, phase, or amplitude of coherent electromagnetic waves....