Photonics Dictionary: G

A telescope objective with excellent spherochromatic correction, consisting of a meniscus crown and a meniscus flint, both convex to the long conjugate.

A beam of light whose electrical field amplitude distribution is Gaussian. When such a beam is circular in cross section, the amplitude is E(r) = E(0) exp [-(r/w)2], where r is the distance from beam...

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...

An intensity distribution (intensity as a function of radial distance from the beam center) which is given by the Gaussian function: where: I0 is the intensity at the beam center r is the radial...

A pulse that has the waveform of a Gaussian distribution.

The masking of all openings of an optical transform -- except the hole at the symmetrical center -- with a thin wire gauze to attain a more precise image.

A type of birefringent polarizing prism that transmits the extraordinary ray and removes the ordinary ray through total internal reflection. It consists of two calcite prisms with an air gap...

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

A galvanometer is an instrument used for detecting and measuring small electric currents. It typically consists of a coil of wire suspended in a magnetic field, with a pointer attached to the coil....

A small mirror, sometimes plane and sometimes concave, attached to the rotating coil of a galvanometer to cause a spot of light to move along a scale.

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 optical power loss caused by a space between axially aligned fibers.

A gas laser wherein the gas mixture is not exhausted into the atmosphere but is continually recycled. It is excited in the active region, cooled and re-excited. The GTL requires no constant gas...

An intensified charge-coupled device that uses a large negative charge at the grid to switch off the flow of electrons at periodic intervals in order to provide a clearer output image when adverse...

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...

1. A faint second image caused by reflection that is sometimes seen when observing through an optical instrument. 2. With respect to spectroscopy, a false image of a spectral line formed by...

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 noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides. Common window or bottle glass is a mixture of soda,...

Property of a surface which, because of directional reflection, is responsible for the degree to which reflected highlights or the images of objects may be seen as superimposed on the surface.

A spectrometer or autocollimator used to measure prism angles.

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...

Gram-positive bacteria are a group of bacteria that have a thick cell wall composed primarily of a substance called peptidoglycan. This thick peptidoglycan layer retains a stain called crystal violet...

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...

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...

An optical device that permits the alignment of a gun, cannon or rocket launcher system with its target.