Photonics Dictionary: F

With respect to a unit cell in a crystal structure, the property defining an atom located at the center of each face.

A grating with very coarse rulings to match the long wavelengths in the far-infrared region. In the most efficient ruling method, grooves are cut in plane, solid aluminum alloy blanks.

A laser with output over a wide range of wavelengths spanning the far-infrared region of the spectrum (30 to 1000 µm); typically, it consists of a metal or dielectric waveguide one to two...

A gas maser that is capable of producing radiation in the far-infrared region of the spectrum.

That part of the infrared spectrum from about 30 to 1000 µm.

A night-vision device that uses one or more infrared transducers to scan a scene in the 3- to 5-µm or 8- to 12-µm spectral region, convert the infrared radiation to electronic data and...

The mathematical formula that proves that any linear operator for which the impulse is known can be wholly characterized according to its impulse response.

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...

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...

A means of determining a prism's index of refraction by placing the prism so that its emergent face is perpendicular to the incident beam. This arrangement permits the determination of the prism's...

A device in which slab geometry internally compensates for thermal-optic distortion; the solid host material -- glass or Nd:YAG -- is in the form of a rectangular slab with plane parallel faces. The...

Data gathered by a facsimile system and converted into graphic, readable form; generally used in meteorology. Also known as fax chart or fax map.

A FAC lens, or fast axis collimation lens, is an optical component used in laser diode systems to collimate the fast axis of laser emission. Laser diodes emit light in two main axes: the fast axis,...

The decrease of a component's efficiency, or a reduction in a material's light sensitivity, as the result of accumulated exposures to radiant energy.

A system designed to control the output quantity of a device by returning a portion of its output signal to its input. This results in the manipulation of the input quantity so that the desired...

A femtosecond laser is a type of laser that emits ultrashort pulses of light with durations on the order of femtoseconds, where one femtosecond is equal to 10-15 seconds. These lasers are capable of...

In microscopy, the measured distance between theoretical parallel lines that are drawn tangent to the particle profile and perpendicular to the ocular scale.

A standard for fiber optic data transmission systems being developed by the American National Standards Institute (ANSI) and associated working groups that will make fiber optic components from...

Fiber joints, also known as fiber optic splices, refer to the connection points where two optical fibers are permanently joined together to form a continuous optical transmission path. These joints...

A fiber laser is a type of laser in which the active gain medium is an optical fiber doped with rare-earth ions such as erbium, ytterbium, or neodymium. Fiber lasers generate coherent light through...

A fiber optic cable assembly refers to a complete unit consisting of optical fibers, connectors, protective jackets, and other components that are assembled together to facilitate the transmission of...

A fiber optic gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in orientation or rotation. It operates based on the principle of the Sagnac effect,...

A fiber optic imaging bundle is a specialized optical device composed of multiple optical fibers bundled together. Each fiber optic strand within the bundle acts as a conduit for transmitting light....

A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It serves as the precursor from which optical fibers are drawn. The process of...

A fiber optic sensor is a device that uses optical fibers to detect and measure physical, chemical, biological, or environmental parameters. Unlike traditional electrical sensors, fiber optic sensors...

A fiber optic spectrometer is a device used for measuring the spectral content of light. It utilizes optical fibers to transmit light from a source to a spectrometer unit, where the light is...

A coherent fiber optic bundle made from fibers whose diameter changes gradually along its length. Used to magnify or reduce the input image.

A fiber optic transceiver, often simply referred to as an "optical transceiver," is a device used in fiber optic communications to transmit and receive data over optical fibers. It integrates both a...

The use of thin flexible glass or plastic fibers as wave guides — or "light pipes" — to channel light from one location to another. Fiber optics is based off of the principle of total...

An optical recording technique that uses light source(s), a beamsplitting cube, light detector(s) and an optical fiber chronically implanted in animal brain to deliver excitation light to neurons...

A microscope in which laser light is delivered through single-mode fibers that replace the pinhole usually used in confocal microscopy. When the Gaussian mode is imaged from the fiber output onto the...

A fiber-coupled LED (light-emitting diode) refers to an LED device that is optically coupled to an optical fiber for the purpose of efficient light transmission. In this configuration, the LED serves...

A fiber-coupled photoconductive antenna (FCPA) is a type of optoelectronic device that combines a photoconductive antenna with optical fibers for the purpose of generating or detecting terahertz...

The field of view (FOV) refers to the extent of the observable world or the visible area that can be seen at any given moment through a device, such as an optical instrument, camera, or sensor. It is...

The angle measured between the focal surface containing the image and a plane normal to the optical axis.

The process whereby the shape of an optical surface is altered by polishing.

In solar energy technology, the percent of usable land covered by collectors. The horizontal collector is the only design that exhibits 100 percent fill factor.

Filoviruses are a family of viruses that are responsible for severe and often fatal hemorrhagic fevers in humans and non-human primates. The name "filovirus" is derived from their filamentous...

A grating used as a reflectance filter, particularly in the far-infrared. Small plane gratings, blazed for the wavelength of the unwanted radiation, are produced for this purpose.

A function used in a convolution filtering operation. The image to be filtered is convolved with the filtering kernel to obtain the enhanced image.

A device that holds a number of filters and allows the filter with the desired characteristics to be rotated into an optical aperture.