Photonics Dictionary

A device used in a free-electron laser to convert the electron-beam's energy into microwave laser radiation by creating a magnetic field of alternating polarity through which the free electrons are...

A doubly refracting crystal having a single axis along which there is an absence of double refraction.

A color space in which equal distances represent equal visually perceived color differences.

In a cathode-ray tube, the region wherein a display on the tube keeps 70 percent or more of its luminance at the center of the viewing area.

Array used in coded-aperture imaging experiments with two-beam CO2 lasers that provide an artifact-free process, faithful reproduction of the true image, and more photon collection than the pinhole...

A three-terminal semiconductor having only one PN junction and a stable, open-circuit, negative-resistance property.

One of the four functions that allows the computation of a transparent medium's index of refraction, provided the index has been identified for four standard wavelengths.

An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot onboard. UAVs are remotely controlled or autonomously operated, and they can be used for various...

Behaving as though characterized by a series of waves having planes of vibration oriented at all possible azimuths.

A resonator often used for mode control in Fresnel number laser cavities that is highly vulnerable to extremely weak external sources of feedback.

A type of glass contrived by Schott that is highly transparent to ultraviolet radiation.

A vacuum chamber is a sealed enclosure from which air and other gases are removed to create a low-pressure environment, typically close to or at a complete vacuum. These chambers are often...

The technique of producing spectrograms in wavelengths beyond 120 nm by the use of a diffraction grating and a Schumann plate in a vacuum environment.

A device that serves to detect the presence of vacuum ultraviolet radiation. It may be photographic film, a thermopile, ion chamber, vacuum photodiode, photomultiplier or channel electron multiplier.

Radiation whose spectrum runs between 100 and 300 nm. Any work with these wavelengths requires evacuated equipment.

Any source that emits radiation of wavelengths between 100 and 300 nm. Instruments used to study these sources must be evacuated, as vacuum ultraviolet does not travel freely in air.

A method of spectral analysis using wavelengths between 100 and 300 nm that utilizes both emission and absorption techniques.

Van der Waals forces refer to the attractive or repulsive forces between molecules (or parts of molecules) that arise from fluctuations in electron distribution. These forces are relatively weak...

An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements so that it emerges from the fixed lens as a large-diameter parallel bundle....

A machine vision technique of image correlation whereby the correlation kernel (template of the desired image) is transformed into a group of vectors, each representing a specific feature of the...

A brightness, superimposed on the image of the retina, that decreases its contrast and that often results in decreased visibility.

The angular relation between two light rays that originated at the same object point. Sometimes used to indicate the angle between the visual axes of the eyes.

With respect to a television system, a pulse transmitted at the end of each field to break off the cathode-ray beam as it begins the next field.

A laser that has a surface-emitting semiconductor gain element coupled to an external mirror designed to complete the laser resonator. VECSELs can be electrically or optically pumped. The extended...

In television system specifications, the number of parallel horizontal black and white lines of equal thickness, that can be resolved from top to bottom of the raster. (One line equals either a black...

With respect to television, the returning direction of the electron beam during the vertical blanking period.

A type of surface-emitting laser diode that uses dielectric mirrors to produce surface emission. The laser cavity is established in a vertical direction with respect to the plane of the active region.

A device that measures the back focal length or vertex power of a lens.

In integrated circuits, a pathway, hole, or other passage through the substrate.

A vibrational transition refers to a change in the vibrational energy of a molecule. Molecules consist of atoms that are connected by chemical bonds, and these atoms are not stationary but are in...

A type of change in the energy levels of molecules in a laser that results in lasing action. Vibronic transitions are those between one electronic level and another.

A test similar to the Knoop hardness test, but used for fractured material. The indenter is a square-based pyramid-shaped diamond.

Referring to the bandwidth and spectrum location of the signal produced by television or radar scanning.

A wideband amplifier used to process video or picture information.

A device, such as a thermionic or crystal diode, that is introduced into the vision channel of a television receiver to select the signal from the intermediate-frequency carrier.

A display standard no longer in use and originally defined for IBM PCs, with 640 3 480 pixels in 16 colors and a 4:3 aspect ratio. There is also a text mode with 720 3 400 pixels. The standard has...