Photonics Dictionary: G

GaN (gallium nitride) distributed feedback (DFB) lasers refer to a specific type of semiconductor laser based on Gallium Nitride materials and designed with a distributed feedback structure. These...

An interferometer similar in construction to a Fabry-Perot interferometer but having a rear mirror with high reflectivity, allowing light to escape only at the partially reflective front mirror.

Temporal jitter at a signal's receiver when amplified noise causes frequency shifts, as with a soliton traveling through an erbium-doped fiber amplifier.

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

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...

Also known as amplification. 1. The increase in a signal that is transmitted from one point to another through an amplifier. A material that exhibits gain rather than absorption, at certain...

Gain-switching is a technique used in lasers to generate short pulses of light by modulating the gain of the laser medium. This method is distinct from Q-switching and mode-locking, two other common...

Gallium arsenide phosphide (GaAsP) is a semiconductor alloy composed of gallium (Ga), arsenic (As), and phosphorus (P). It is commonly used in the fabrication of optoelectronic devices, particularly...

Gallium nitride (GaN) is a compound made up of gallium (Ga) and nitrogen (N). It is a wide-bandgap semiconductor material that exhibits unique electrical and optical properties. Gallium nitride is...

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...

Modification of a system to provide for a linear transfer characteristic from an input to an output device. A circuit for this purpose is built into a television camera to compensate for display tube...

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...

A technique for measuring the concentration of any gases. Identical infrared beams are alternately chopped, one passing through a reference cell and the other passing through a cell with the gas...

An electron tube whose current flow is affected by the pressure on the gas or vapor contained in the tube.

In detectors, the ability to switch on and off electronically, thus producing the effect of a mechanical shutter.

The area of optics that deals with the propagation of Gaussian laser beams in free space, or any general medium - i.e. lenses- under the paraxial (small divergence angle) approximations. Gaussian...

1. That branch of optics that illustrates the theory in which q is substituted for sin q in Snell's law. Effective results are achieved if the aperture and field angle are made very small. The...

A specific gas-filled tube designed to illustrate the luminous effects of discharges through rarefied gases.

Trade name referring to an instrument that determines surface distances by measuring the length of time it takes for a modulated lightwave to reach a mirror and be reflected to its point of origin.

The physical center of the lens; it is on the axis of the lens, halfway between the front and rear vertex. It is sometimes referred to as the mechanical center of the lens.

The position and shape of the image of a point source, as predicted by geometric optics alone. The geometric image is to be differentiated from the diffraction image, which is determined from...

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...

The area of optics in which the propagation of light is described by geometrical lines (or rays) governed by Fermat's Principle. Geometrical optics is useful as long as the objects in which the light...

The superposition of satellite or aerial images with a map in order to process and remove distortion. Uses reference points from map to align and apply information.

Germanium crystal refers to a crystalline form of the element germanium (Ge), which is a metalloid and semiconductor commonly used in various electronic and optical applications. Germanium crystals...

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...

GigE, short for gigabit Ethernet, refers to a standard for high-speed Ethernet communication, capable of transmitting data at rates of up to 1 gigabit per second (Gbps), or 1000 megabits per second...

A furnace used to heat glass materials. It may be a small laboratory-type furnace for small-scale experiments or large enough to hold gas-fired tanks for the commercial mass production of glass....

A photometer for measuring gloss by comparing the specular reflectance to that from a perfect specular reflector.

The graphed curve illustrating the directional reflectance of a sample for different angles of collection.

The term gradient-index profile refers to a specific type of refractive index distribution within an optical material. In optics, the refractive index of a material describes how much the speed of...

In a microscope, the diaphragm located between the Bertrand lens and the eyepiece, which is closed during conoscopic viewing to restrict the interference figures to that of a crystal lying on the...

Gram-negative bacteria are a group of bacteria that possess a cell envelope composed of a thin layer of peptidoglycan surrounded by an outer membrane. This outer membrane contains lipopolysaccharides...

Graphene is a two-dimensional allotrope of carbon consisting of a single layer of carbon atoms arranged in a hexagonal lattice pattern. It is the basic building block of other carbon-based materials...

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...

A grating beamsplitter is an optical device that utilizes the principles of diffraction to split a beam of light into multiple beams, often redirecting them at specific angles. It is based on the...

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...

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...

A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...

A term variously applied to remote sensing techniques that essentially refers to all parametric conditions that influence the sensor system; includes the quantitative reality that the sensor sees and...

A wave in which energy is focused near a boundary separating materials having different properties. Propagation of the wave is in a direction parallel to the boundary.

Gyroscopy refers to the principles and applications of gyroscopes, devices that measure or maintain orientation based on the principles of angular momentum. Gyroscopes are essential in various...