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Photonics Dictionary: P

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peta-; poise
P-type conductivity
In a semiconductor, the state created by the addition of a dopant that creates excess holes.
P-type material
A semiconductor material in which the dopants create holes as the majority charge carrier. It is formed by doping with acceptor atoms.
power amplifier
private automatic branch exchange
paraxial/axial color
The finite amount of electrical charge generated in response to incident radiation and transferred from one storage element to the next in a charge-coupled device. Each packet corresponds to a pixel...
packet switching
The transmission of data in groups (packets) of information~comma~ each handled as an aggregate.
packing density
1. In a photonic interconnect, the number of detectors in a given area. Detectors spaced too closely may give rise to crosstalk. 2. In the cross section of a fiber optic bundle, the ratio of fiber...
packing fraction
The ratio of the active core area of a fiber bundle to the total area at its light-emitting or receiving end.
picture archiving and communications system
photoacoustic imaging
pair production
The production of a positron-electron pair by a photon having energy greater than one mega-electron-volt, whereby some of the photon energy is converted to the rest mass of the pair.
In interlaced television scanning, an effect in which the lines of one field fail to fall exactly within the lines of the following field, both fields comprising one frame of the picture. The lines...
phase alternation line
pulse amplitude modulation
pulse address multiple access
panchromatic photographic film
Black and white film that has a wavelength sensitivity similar to that of the eye.
panchromatic sensitivity
Color sensitivity extended to cover the entire visible spectrum out to the red.
panoramic camera
A camera designed to form a continuous record of an expansive section of the horizon. The typical panoramic camera is mounted to rotate about a vertical axis. A slit opening in the film plane and the...
panoramic distortion
The image distortion produced by a panoramic camera with a swinging lens or a swinging mirror in front of a fixed lens. The magnification is greatest in the center and diminishes to each side in the...
panoramic lens
A lens system that is capable of producing a 360° image, or one that is very close to that. In recording, the image may be formed on a curved strip of film surrounding the lens, resulting in a...
panoramic telescope
A telescope so manufactured that the image remains erect and the position of the eyepiece is unchanged as the line of sight is pointed in any horizontal direction.
photosynthetically active radiation
parabolic mirror -> paraboloidal mirror
A concave mirror that has the form of a paraboloid of revolution. The paraboloidal mirror may have only a portion of a paraboloidal surface through which the axis does not pass, and is known as an...
parabolic profile
The condition in which the index of refraction in an optical fiber varies as a parabolic function of the radius.
paraboloidal condenser
A condenser composed of a paraboloidal reflector and used for dark-field illumination.
paraboloidal mirror
A concave mirror that has the form of a paraboloid of revolution. The paraboloidal mirror may have only a portion of a paraboloidal surface through which the axis does not pass, and is known as an...
paraboloidal reflector -> paraboloidal mirror
A concave mirror that has the form of a paraboloid of revolution. The paraboloidal mirror may have only a portion of a paraboloidal surface through which the axis does not pass, and is known as an...
paraffin oil
A saturated compound of carbon and hydrogen used as a liquid coating material for optical components in high-power laser applications. See liquid coating.
parallactic angle
The angular difference in the direction of an object as seen from two points of observation. The angle subtended at the object by the base length of a rangefinder.
The optical phenomenon that causes relative motion between two objects when the eyepoint is moved laterally. When parallax appears in a telescope between the image and reticle, this indicates the...
parallax panoramagram -> stereo projector
A projector designed to give each of the observer's eyes its own disparate image.
parallel beam -> collimated radiation
Radiation in which every ray from any given object point can be considered to be parallel to every other. This is never completely the case: The light from a star is really diverging, and all...
parallel processing
In imaging, the processing of pixel data in such a way that a group of pixels is analyzed at one time rather than one pixel at a time.
parallel scanning
Parallel scanning refers to a method of acquiring data or images simultaneously from multiple sources or in parallel, rather than sequentially scanning each source one after another. This approach is...
parallel transmission
A mode of data transmission whereby bits of information are carried simultaneously at different frequencies over a single channel.
parallel-plate waveguide
A pair of waveguides with axes normal to the plane and that guide uniform cylindrical waves.
parallel/serial converter
A device that converts data transmitted in the parallel mode to a sequence of bits at a single frequency for output in the serial mode.
parallelogram distortion
In a camera or cathode-ray tube, distortion that is designated by a lateral skewing of the reproduced image.
parametric amplification
Means of amplifying optical waves whereby an intense coherent pump wave is made to interact with a nonlinear optical crystal to produce amplification at two other optical wavelengths. See parametric...
parametric oscillator
A device using a parametric amplifier inside a resonant optical cavity to generate a frequency-tunable coherent beam of light from an intense laser beam of fixed frequency. This device is tuned by...
parasitic oscillation
Oscillation in rod and disc amplifiers that critically limits the achievable energy storage.
Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.
paraxial focus
Focus derived from paraxial data.
paraxial ray
A ray that behaves according to paraxial equations; one that lies close to and almost parallel to the optical axis.
Description of an optical system in which all the elements are aligned on the same axis.

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