Photonics Dictionary

An optically pumped solid-state laser in which the active medium is a neodymium ion in a glass rod host. Abbreviated Nd:glass.

Ink used for writing on glass, and also for blackening the edges of lenses to prevent reflection. In the latter case, the refractive index of the ink must closely match that of the glass.

A spectrograph having glass as its refracting component and used in cases where speed and high dispersion are not required. The glass material has a range of about 3700 to 8000 Å.

A type of glass used in telescope mirrors, formed by adding a nucleating agent to standard glass and then heating it until it crystallizes.

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....

The process whereby a spectacle lens is placed in a frame.

The plane shared by the pair of axes in a twin crystal.

The specular reflection of individual parts of a surface.

A controlled random search process, such as generalized simulated annealing, that has been incorporated into many optical design programs as a way of helping designers find the most suitable lens...

The total radiation, both solar and diffuse sky, that is incident to a unit's horizontal surface.

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

A crystal of microscopic size having no definite plane faces and having a globular shape. At the time the crystal is formed, the strong surface tension influences the formation of the plane faces.

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

An electric discharge in a low-pressure gas having a low-current density and a space potential near the cathode that is much higher than the ionization potential of the gas but less than its sparking...

A lamp in which the ionization of the inert gas contained in it produces a glow in the space close to the negative electrode.

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...

Gold colloid aggregates refer to clusters or assemblies of gold nanoparticles suspended in a liquid medium. These aggregates are formed when individual gold nanoparticles come together due to various...

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 Golgi staining technique (also called the black reaction) makes it possible to look at the nervous system by rendering neurons visible under light microscopy. After a long process involving...

A spectrometer or autocollimator used to measure prism angles.

An eyepiece having a rotating index or cross wire linked to an external 360° scale to allow measuring of angles in an image.

A device used to measure directional reflectance, with light collection restricted to a narrow range of angles of which the central angle varies.

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

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

Descriptive of an optical fiber having a core refractive index that decreases almost parabolically and radially outward toward the cladding. This type of fiber combines high bandwidth with moderately...

A mirror whose percent reflectance varies as a function of position on the mirror surface.

In image processing and machine vision, the rate of change of pixel intensity.

Edge enhancement with a directional characteristic.

In an image, the orientation and magnitude of the rate of change in intensity at any point.

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 multicrystalline material, the meeting point between crystallites.

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...

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...

Unit of mass in the SI system.

An electron tube having two electron guns, one on each side of the storage medium, to encode the information onto the medium, and to read and simultaneously erase the electrostatic encoding.