Photonics Dictionary: F

The product of Avogadro's constant and the electrical charge of an electron; thus, the electrical charge carried by 1 gmol of a substance, or approximately 9.65 x 104 C.

In a birefringent material, the index of refraction varies with the direction of vibration of a lightwave. That direction having a low refractive index is the fast axis; at right angles to it is the...

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,...

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 crystal capable of being polarized in the reverse direction when an electric field is applied.

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...

A photodetector employing photoregeneration of carriers in the channel region of an FET structure to provide photodetection with current gain.

An aperture located at an image plane of an optical system that determines the size and shape of the image.

The principal point of a lens relative to the object space.

The spectral transmission window in silica-based fibers between 830 and 850 nm.

The separate spectral lines formed by a diffraction grating that are characterized by one wavelength difference in path length between adjacent slits.

The process of grinding the concave surface of a single-vision spherical lens.

The process of grinding the toric surface of a single vision sphero-cylindrical lens.

The distance between the locating surface of the lens mount and the image plane.

Flow chemistry, also known as continuous-flow chemistry, is a chemical manufacturing process where reactions take place in a continuous stream of fluids (liquids or gases) rather than in batch...

A device, also called a fluorescence lifetime instrument, that measures decay curves of fluorescing samples. It generally consists of a gated pulsed flashlamp or a cavity dumped dye laser...

Förster resonance energy transfer (FRET) is a mechanism describing the transfer of energy between two closely spaced fluorescent molecules. This phenomenon is named after the German scientist...

The Foucault test is performed by moving a knife edge laterally into the image of a small point source. The eye, or a camera, is placed immediately behind the knife edge, and the exit pupil of the...

The distance between the front focal point and the vertex of the front surface.

Light leakage at a total reflecting interface when another highly refractive medium is brought close to it.

The series of rings when monochromatic light passes through a Fabry-Perot interferometer.

A multiple-beam interferometer, usually consisting of two flat plates, with high reflective ability. The plates are set parallel to one another by spacers so that lightwaves may bounce back and forth...

A laser oscillator in which two mirrors are separated by an amplifying medium with an inverted population, making a Fabry-Perot cavity. Standard diode lasers are Fabry-Perot lasers.

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

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.

The conversion of a still picture into sound waves and its subsequent transmission by radio.

The maintenance of the same scanning relationship between the transmitting scanning spot and receiving scanning spot for each scanning line transmitted in a facsimile system.

A set of rays through a lens originating at a common point and contained in one plane.

The distribution of one signal to more than one location. In a digital computer, it refers to the number of outputs that can be fed by a particular logic circuit.

The object distance at which the eye is focused with the eye lens in a neutral or relaxed state.

The diffraction pattern of a source such as a light-emitting diode, injection laser diode or the output end of an optical waveguide observed at an infinite distance from the source.

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...

The Faraday effect, named after the English scientist Michael Faraday, is a phenomenon in physics where the polarization plane of light is rotated when the light passes through a transparent medium...

A type of mirage that creates a distorted vertical image of relatively flat objects so that they appear as mountains, cliffs, columns or castles. The nonexistent mountainous region in the Arctic...

The fiber optic connector standard for Nippon Telephone & Telegraph (NTT) installations, developed with Nippon Electric Co. (NEC).