Photonics Dictionary: F

An f-theta lens, also known as an f-theta scan lens or simply an f-theta lens system, is a specialized optical component used in laser scanning systems, particularly in laser marking, engraving, and...

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.

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 placement of a device or an additional circuit into a feedback control system to improve its response in relation to a specific characteristic of the system.

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 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...

A method of terminating optical fibers by forming a lens directly on the end of the fiber, eliminating the need for precise end-to-end placement or epoxy sealing in fiber connections.

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

1. A lens situated at or near the plane of an internal image to project the aperture of a previous objective or erector upon the aperture of a following lens. 2. A lens at or near the plane of a...

Secondary aberrations remaining after the primary (Seidel) aberrations have been corrected.

A transformer that is designed to regulate the amount of current that passes through an electron tube's filament.

A method used to produce precision spherical and aspheric molded glass lenses without grinding or polishing.

A type of wide-angle lens that has an angular field above 140° and that exhibits barrel distortion. The most commonly used fish-eye lenses have a field of about 180°, though they are...

A filter, partially opaque to near-ultraviolet, visible and infrared radiation, that may be made by exposing and processing photographic film. Such materials are almost equally opaque to radiation of...

A sensitometer that utilizes an electronic flashtube or a photoflash lamp as both the light source and the shutter for obtaining short-duration exposures.

A lens that focuses on a flat plane because its field of curvature is close to zero.

Floquet-Bloch oscillations refer to a phenomenon in condensed matter physics, specifically in the context of periodic potential systems subjected to an oscillating external field or periodic...

A fiber optic device that uses a HeNe laser, beamsplitter, monochromator and photomultiplier to detect trace levels of chemicals and viruses in samples inside or outside the body.

A lens having an extremely high aperture and used in the recording of x-ray fluorescent screen images. It often is specially designed for the camera, the color of the light and the image...

A form of image intensifier designed to amplify a weak fluoroscopic image. The image is received at an input phosphor screen, as opposed to the light-sensitive electrode emitter used in regular image...

Flux per unit area measured normal to the direction of propagation of the flux.

The application of ultraviolet, x-ray, infrared and conventional photography to law enforcement.

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...

A hologram formed by the recording of a plane object situated in the focal plane of a lens so that each object gives rise to a parallel beam of light incident on the plate. A collimated reference...

An instrument using a Michelson interferometer, a beamsplitter, two plane mirrors and a detector to give Fourier analysis of the detector signal to provide the desired spectrum.

Any of the various methods of decomposing a signal into a set of coefficients of orthogonal waveforms (trigonometric functions).

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin piece of transparent material, typically plastic or glass. This design...

A piece of uniform birefringent material placed at a 45° angle to the plane of polarization in a polarizing microscope to indicate changes in color caused by interference when a birefringent...

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...

An optical resonator in which feedback is accomplished by two parallel planes. In diode lasers, the planes are obtained by cleaving, polishing, etching, etc.

A nonabsorbing, multireflecting device, similar in design to the Fabry-Perot interferometer, that serves as a multilayer, narrow-bandpass filter.

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.

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 highly reflective mirror that is usually flat on one surface and curved on the other, and that has silver, gold or aluminum deposited on glass, providing about 99 percent reflection.

The spectroscopic analysis of interference patterns using a monochannel spectrometer, spectrograph or multichannel spectrometer with a Fabry-Perot interferometer to record the fringes.

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...

1. One of the plane-reflecting surfaces on a multisurfaced polygon. 2. The cleaved end mirror of a laser diode's active region.

The degradation of the facets in a laser diode due to the intensity of radiation.