Photonics Dictionary: P

A thin film or coating that forms on various finished surfaces. On optical surfaces it usually denotes aging.

Photoconductive antenna (PCA) is a semiconductor element that generates or detects high-frequency electromagnetic signals. Compact PCAs based on gallium arsenide (GaAs) or indium gallium arsenide...

Photodynamic inactivation (PDI) is a therapeutic approach that utilizes the combination of light, a photosensitizer, and molecular oxygen to induce cell death or inactivate microorganisms. This...

A medical technology that uses lasers or other light sources in combination with photosensitizing drugs to treat cancerous tumors.

Low-insertion-loss fiber coupler fabricated from a sheet of light-sensitive material laminated onto a fused quartz substrate and exposed through a suitable mask. After development of the plastic...

A device used in the sputtering of thin films, in which a magnet system on the back of the cathode deflects the electrons, lengthening the ionization path. The accelerated ions transfer their...

The determination of a substance's identity or quantity through the analysis of its optical rotation. For example, the examination of crystals and polymers under polarized infrared radiation is very...

A tough, durable, heat- and cold-resistant optical quality plastic used in injection-molded items such as streetlight lenses, automotive taillights and audio compact discs.

Light that is a mixture of wavelengths.

A polygonal mirror, also known as a multifaceted mirror or facet mirror, is a type of optical component used in various laser systems, optical scanners, and imaging devices. It consists of a flat or...

The instrument used to analyze a pulsed electromagnetic wave to determine its time, amplitude, duration and shape, and to display this information in some appropriate form, either visually or...

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...

A condenser composed of a paraboloidal reflector and used for dark-field illumination.

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...

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 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...

A mode of data transmission whereby bits of information are carried simultaneously at different frequencies over a single channel.

In a camera or cathode-ray tube, distortion that is designated by a lateral skewing of the reproduced image.

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...

Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.

Particle acceleration refers to the process by which charged particles, such as electrons or protons, gain kinetic energy and increase their velocity. This acceleration can occur in various natural...

An array of lines in the infrared region of the emission spectrum of atomic hydrogen. Their wave numbers are expressed by the equation: where represents the wave number in the reciprocal centimeters,...

A passive optical network (PON) is a telecommunications network architecture that uses optical fibers and passive optical components to provide high-speed broadband services to end-users. In a PON...

An LCD that has pixels with no internal drive transistors.

An OLED display formed by creating an array of OLED pixels connected by intersecting anode and cathode conductors arranged in rows and columns. Electrical power is passed through selected pixels by...

A pathogen is a biological agent, such as a virus, bacterium, fungus, protozoan, or parasite, that causes disease in its host organism. Pathogens have the capability to invade host tissues,...

A device that determines the lens shape in the cutting or edging phase of fabrication. It also is used to denote the arrangement of markings on a reticle.

A prism made up of two air-spaced components. It has the ability to revert, and not invert, an image, and can be used in convergent, divergent and parallel light. May be rotated to compensate for...

A thin, stretched plastic membrane cemented to a rigid supporting ring. It may be coated to act as a beamsplitter, for example, in a color camera; it is so thin that no perceptible image doubling...

A Peltier cooler, also known as a thermoelectric cooler (TEC) or thermoelectric module, is a solid-state device that uses the Peltier effect to transfer heat between two electrical junctions. It can...

In astronomy, the main lobe of an antenna pattern that has a small angular extent in two mutually perpendicular directions. Invisible in space, it would resemble a searchlight beam.

A standard source of high-charge-state ions for accelerators that has an external magnetic field oriented perpendicularly to the two cathode faces. Also called Philips ionization gauge.

A five-sided prism containing two reflecting surfaces at 45° to each other, and two refracting faces perpendicular to the entering and emerging beams. The deviation angle of 90° is...

A source of light will not cast a distinct shadow of an interfering, opaque object, but will cast a shadow having two parts: 1. the umbra, or the central, totally dark part of the shadow; and 2. the...

A theoretical, ideal lens capable of producing perfect images. Used as a lens design and analysis tool to image collimated output from an afocal system.

The analysis of retinal zones in which different hues can be detected. Also called campimetry.

An optical instrument designed to displace the line of sight in a vertical direction. For submarines and other military uses the periscope is a long tube containing prisms at both ends and...

Typically represented by the Greek letter μ, magnetic permeability is the measure of a material's ability to generate and sustain a magnetic field within itself when an external magnetic field is...

The term perovskite refers to a specific crystal structure commonly found in various materials. Perovskite structures have a cubic arrangement of oxygen ions, forming a framework within which other...

The distortion that is the result of viewing a print from a point other than the center of perspective. The center of perspective is that viewpoint at which the angular subtenses of points in the...

A microscope equipped with a polarizer, an analyzer and a Bertrand lens to focus on the upper focal plane of the objective. It is used chiefly by mineralogists and crystallographers for...