Photonics Dictionary: I

An alien, electrically charged atomic system in a solid; an ion substituted for the constituent atom or ion in a crystal lattice, or located in an interstitial site in the crystal.

In the context of optical materials, the term "impurity level" refers to the presence of foreign atoms or molecules within the material that deviate from its regular or intrinsic composition. These...

That state determining that two waves of like frequency will travel through their maximum and minimum values of the same polarity simultaneously.

In its natural or original position.

In vitro is a Latin term that translates to "in glass." In scientific contexts, particularly in biology and medicine, it refers to experiments or procedures conducted outside of a living organism,...

In vivo is a Latin term that translates to "within the living." In scientific contexts, particularly in biology and medicine, it refers to experiments or observations conducted within a living...

The formation of a hologram by single reference-beam interferences with waves that are diffracted or scattered from a small object.

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

A lamp that emits light when an electric current passes through a resistant metallic wire situated in a vacuum tube.

Flux incident per unit area of a surface.

An exposure meter designed to measure the light striking an object and used at a suitable location in a scene.

A ray of light that falls upon or strikes a surface of an object such as a lens. It is said to be incident to the surface.

The presence, within the body of the glass, of extraneous or alien material. See seed; striae.

In optics, the term denoting the lack of a fixed phase relationship between two waves. If two incoherent waves are superimposed, interference effects cannot last longer than the individual coherent...

A bundle of filaments of optical glass or other transparent materials that transmit only light, not optical images. The arrangement of the individual fibers in the bundle is not sufficiently regular...

The production of holograms initially from either conventional photographs or incoherent optical equipment.

A thermal source that emits less radiation than a blackbody under identical temperature conditions.

A flaw deliberately introduced into an optical fiber to prepare it for cleaving.

The decrease in the refractive index at the center of a fiber's core, caused by certain fabrication techniques. Also called profile dip.

The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.

In an optical waveguide, the refractive index as a function of radius.

A laser diode with an output beam contained in the active layer by means of a built-in refractive index profile formed in that layer or in the adjacent cladding layers or both.

A material, often a liquid or cement, whose refractive index is nearly equal to the fiber's core index, used to reduce Fresnel reflection from a fiber end face.

Generally, a rotatable table with scales marked in degrees. The fiducial marking also may be a vernier scale. The same scheme is applied to linear movement. Such devices are often applied to...

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...

An energy transition concerned with the combination of a photon and a phonon.

Metal used in components of the crystalline semiconductor alloys indium gallium arsenide (InGaAs), indium gallium arsenide phosphide (InGaAsP), and the binary semiconductor indium phosphide (InP)....

A semiconductor material that is used as an infrared detector for light up to 5 µm in wavelength.

An InGaAs (indium gallium arsenide) camera is a type of imaging device that utilizes InGaAs sensors to capture images in the near-infrared (NIR) spectrum. InGaAs is a semiconductor material that is...

Indium phosphide (InP) is a compound semiconductor material composed of indium (In) and phosphorus (P). It belongs to the III-V group of semiconductors, where elements from groups III and V of the...

A material widely used as a transparent conductive coating.

Induced pluripotent stem (iPS) cells are ordinary cells that are genetically reprogrammed to an embryonic stem cell-like state to allow the human cells to be used for therapeutic purposes....

A device used in thin-film deposition; the material to be evaporated is placed in a crucible that is heated inductively by current passing through a coil around it.

A device used to accelerate the electrons in a free-electron laser by supplying electrical energy to the electron beam through a series of transformers.

A shutter in which the opening and closing times for a large aperture setting occupy a substantial fraction of the total exposure time so that apertures and time pair readings from an exposure meter...

Inertial confinement fusion (ICF) is a method of achieving nuclear fusion, a process where two atomic nuclei combine to release energy. In the case of inertial confinement fusion, the fusion reaction...

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...

A mirage that consists of an image of an object appearing below its true position as the result of abnormal refraction by the atmosphere between the object and the viewer. It is the opposite of a...

An unbounded quantity, an indefinitely large number. Infinity is commonly expressed by the symbol ∞.

In a microscope, a space reserved to accommodate an optical filter or polarizer.

Infrared radiation absorbed by crystals as a result of the excitation of lattice vibrations in which ions having opposite charges move relative to one another. These vibrations take place in a narrow...

A system that uses infrared detectors and related instrumentation to determine when abnormal amounts of infrared radiation, usually in the form of heat, are present in an area; used for the detection...

The study and the interpretation of the infrared emittances of celestial bodies and phenomena.

A thermal infrared imaging procedure developed for quality control of printed circuit boards. The thermogram of each board under test is compared with a standard thermal profile and then with a...

An infrared source, set in a stationary position, that is used as a reference in certain navigational systems.

An instrument, similar in design to regular binoculars, that can transmit and enlarge infrared images.

A superconducting bolometer, operating at very low temperatures, that is used to detect infrared radiation.

An infrared camera, also known as a thermal imaging camera or IR camera, is a device that captures and visualizes the infrared radiation emitted by objects, revealing temperature variations across...

An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible spectrum of light. These detectors are utilized in various applications,...