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break current
The point at which decreasing current supplied to a laser results in the extinguishing of the laser discharge.
breakdown voltage
In avalanche photodiodes, the point at which an increase in the reverse bias voltage causes the current gain to approach infinity.
breakout cable
A breakout cable, also known as a fan-out cable or breakout assembly, is a type of cable that combines multiple individual cables into a single, larger cable. The breakout cable is designed to...
Breit-Wigner formula
Theoretical calculation of the cross section for a nuclear reaction given in the vicinity of a single resonance level in the compound nucleus.
bremsstrahlung
Electromagnetic radiation that is emitted by an electron as it is accelerated or decelerated while moving through the electric field of an ion.
Brewster angle window
A parallel plate of glass in such a position that the refracted and reflected rays of incident parallel light are mutually perpendicular. In this situation the reflected light is plane polarized, and...
Brewster's angle
For light incident on a plane boundary between two regions having different refractive indices, the angle of incidence at which the reflectance is zero for light that has its electrical field vector...
Brewster's fringes
The fringes used in the Jamin interferometer and produced by light that has been internally and externally reflected by two plane-parallel plates, inclined toward each other at a small angle.
Bridgman technique
Crystal growth method that resembles static freeze, but that induces growth by removing the ampoule from the furnace so that the freezing-point temperature gradient is unchanged during the growth...
bright-field illumination
The illumination generally used in microscopy, whereby the specimen appears dark against a light background.
bright-field image
An optical image having a brightly lit background.
bright-line spectrum
An emission spectrum consisting of bright bands against a dark background.
brightfield
Brightfield refers to a type of microscopy and imaging technique in which the specimen is illuminated with a white light source, and the image is observed or captured against a bright background. In...
brightness -> luminance
Luminous flux emitted from a surface per unit solid angle per unit of area, projected onto a plane normal to the direction of propagation. Also known as brightness and luminous sterance.
brightness control
The manual shifting bias control of a cathode-ray tube that determines both the average brightness and the contrast of a picture.
brightness meter
An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...
brightness resolution
The degree to which a pixel in a digital image represents the analog brightness of the corresponding point in the original image. It is dependent largely on the number of bits devoted to representing...
brightness scale
A graduated range of stimuli perceived as having equivalent differences of brightness.
Brillouin scattering
Brillouin scattering is a phenomenon in physics where an incident electromagnetic wave (usually light) interacts with acoustic phonons (quantized lattice vibrations) in a material, resulting in the...
bring-in
The final correction of a polished surface or of an angle to the specified precision.
broadband
Indicating a capability to deal with a relatively wide spectral bandwidth.
broadband dielectric mirrors
Broadband dielectric mirrors, also known as broadband mirrors, are optical coatings designed to efficiently reflect or transmit light over a broad range of wavelengths. These mirrors are constructed...
broadband filter
A broadband filter is an electronic or electromagnetic device designed to pass a range of frequencies or signals within a specified bandwidth while attenuating or rejecting signals outside of that...
broadband incident radiation -> white light
Light perceived as achromatic, that is, without hue.
broadside radiation
Radiation that occurs perpendicular to the plane of the radiation device.
broken edge
A chamfer or protective bevel.
bronchoscope
An optical instrument designed to permit the visual examination of the interior of the bronchi.
Brownian motion
The behavior of microscopic solid particles suspended in a fluid, first observed by botanist Robert Brown in 1827 as a continuous random motion.
Brucke loupe
A telemicroscope in which a negative eyepiece is used to produce erect images.
bubble chamber
A large tank filled with liquid hydrogen, with a flat window at one end and complex optical devices for observing and photographing the rows of fine bubbles formed when a high-energy particle...
bubble chamber optics
Specially designed optics for the observation and photographing of hydrogen in a bubble chamber.
bubble chamber photography
The photographic recording of gas bubbles produced when particles traverse liquid hydrogen in a bubble chamber.
bubble memory -> magnetic bubble film
An amorphous film in which cylindrical bubbles of reverse magnetization can be formed to follow circuit paths usually made by depositing magnetic metal strips on the film surface. It is used in...
bubble writing -> beam-addressable technology
The application of reversible writing with a laser beam on particular storage materials. In one method, an amorphous film is heated and then crystallized for writing. Bubble writing involves the...
buckyballs -> fullerenes
Molecules composed entirely of carbon, in the form of a hollow sphere, ellipsoid or tube. Also called buckyballs. Cylindrical fullerenes are called carbon nanotubes or buckytubes.
buffer
1. In fiber optics, a protective material applied as an optical fiber cover that has no optical function. 2. In image processing, a peripheral that stores data between two active processing stages.
bulk acoustic wave
A sound wave that travels through a piezoelectric material.
bulk nonreciprocal device
A device that functions throughout the continuous radiation of a linearly polarized plane wave, and whose nonreciprocity arises from the Faraday rotation of linearly polarized radiation.
bulk scattering
The scattering of light within a medium.
bump-forming optical disk -> dye-polymer optical disc
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...
bundle
A conical or cylindrical package of light rays emanating from a common point on the object.
Bunsen screen
A photometer screen that contains a diaphragm of paper or parchment with a translucent central spot of oil or paraffin.
Bunsen-Roscoe law
The law stating that the amount of chemical change produced is proportional to the amount of light absorbed. Actually, the change is also dependent on the intensity of light -- a fact named the...
burn
A surface imperfection caused by a polisher running dry too long. It occurs with felt or plastic polishers, and may appear as a reddish brown.
burn-in
The operation of a laser diode or other component prior to its use in its intended application, as a means of testing and stabilizing it.
burn-through
A detector's ability to sense an object on the opposite side of a thin but opaque barrier such as cardboard.
burning glass
A convex lens that brings an incident bundle of rays to a focus to produce intense heat at the focus.
burnishing
The process of lapping a thin edge of metal over the bevelled edge of a lens to maintain it within its cell.
burst mode laser
A high-frequency pulse-rate laser with an output limited by the heat capacity of the laser medium. Instead of having continuous cooling, the laser operates until the medium reaches a maximum...
burst pressure
The measure used in vacuum technology to quantify the total pressure capacity of the ferrofluidic seal before it fails.

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