Photonics Dictionary: D

The theory established by Christian J. Doppler in 1842 that states that the rate of change in distance between a perceiver and a radiation source determines the change in frequencies.

The principle stating that the displacement of spectrum lines is determined by the distance between, and relative velocity of, the observer and the light source. When distance decreases, the lines of...

An imaging process, similar to specific Doppler mapping radar techniques, that utilizes a laser, an optical imaging system, and a line array of photodetectors and spectrum analyzers. The laser...

A display format consisting of small light-emitting elements arranged as a two-dimensional array. Various elements are energized to depict a character. The typical matrix is 5 x 7 dots.

The separation of unpolarized light into two plane-polarized elements by a doubly refracting crystal. When a crystal, such as calcite, is placed between the eye and a pinhole in a card, two bright...

A defect of a binocular instrument causing two images to be seen separately instead of being fused. It is caused when the optical axes of the two telescopes are not parallel. In minor cases, the eyes...

A spectrophotometer in which the beam emitted by the radiation source is split into beams that travel through the sample and a reference cell and are subsequently recombined to fall on the detector....

Double-clad fiber (DCF) is a specialized optical fiber that features two concentric cladding layers surrounding a core. The design of double-clad fibers allows them to be used in various...

A method of fabricating an optical waveguide by melting the core and clad glasses in two suitably joined concentric crucibles and then drawing a fiber from the combined melted glass.

A type of transversely excited laser with a uniform arc-free discharge of large cross-sectional area that can be scaled to very large systems.

The formation of an interferogram by means of two holograms on the same recording medium, often used for determining small changes in an object. One hologram produces a primary image that constitutes...

A mass spectrometer utilizing both radial electrostatic and magnetic field analyzers to improve the focusing and increase resolution.

A fast, wide-angle lens used in television and photographic cameras, with excellent overall correction, but subject to residual oblique spherical aberration.

A device used to create a light output that exceeds light input, the energy being provided by an electric field. It consists of a photoconductive layer with an electroluminescent layer between plates...

A CRT screen on which two phosphors differing in color and persistence are deposited.

1. A compound lens consisting of two elements. If there is an air space between the elements it is called an "air-spaced doublet.'' If the inner surfaces are cemented together, it is called a...

A form of prism invented by H.W. Dove. It resembles half of a common right-angle prism in which a ray entering parallel to the hypotenuse face is reflected internally at that face and emerges...

A system for fabricating optical fiber, consisting of a furnace that heats the materials, a polymer coating stage, a capstan-pulling apparatus that free-draws the preform into a fiber and a drum on...

A gradual change in the output of a circuit or instrument over time.

A technique used in astronomy that requires a radio telescope to be directed at a point in the sky west of the object under observation. The Earth's rotation causes the object to drift through the...

An astronomical scanning technique for capturing images of stars without moving the sensor. To perform a drift scan, a CCD sensor's readout rate must be synchronized with the motion of celestial...

The hardware for reading (and writing in devices so equipped) an optical mass data storage disk.

A type of streak camera that uses film wrapped around a drum, which moves at a constant speed to record the changing shape of a short-lived event, such as a lightning flash.

An image-processing device that scans in a straight line parallel to the axis of a rotating cylinder to which the material to be recorded is affixed.

A gas laser equipped with Brewster windows and concave mirrors (having unlike reflective properties) at each end of the tube to produce two separate wavelengths at the same time.

A material's ability to undergo plastic deformation, specifically elongation, without fracturing.

Propagation of electromagnetic waves through the Earth's atmosphere in a path that conforms to the curvature of the Earth due to atmospheric thermal inversion. Regions of the atmosphere act as a...

In data communications, the simultaneous operation of a circuit in both directions is known as full duplex; if only one transmitter can send at a time, the system is called half duplex.

A laser using a dye solution as its active medium. Its output is a short pulse of broad spectral content and its achievable gain is high. Dye lasers function at room temperature. Synchronous pumping...

A type of erasable data storage device that uses a medium deposited on the disc in two layers, each dyed to absorb a different wavelength of laser light. To record data, the lower layer is heated by...

Stress applied to an optical fiber at a constant rate.

An optical correlator incorporating a binary phase-only spatial light modulator made from an iron garnet magneto-optic solid crystal and used in target recognition systems.

The theoretical explanation and analysis of the interactions between electron waves and crystals used in studying electron diffraction.