Photonics Dictionary: P

A device for measuring absorption coefficients in which a confined, nonabsorbing gas fills the space inside the cell between the two windows, which are made from a weakly absorbing medium.

The transmission of data in groups (packets) of information~comma~ each handled as an aggregate.

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.

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...

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...

A mounting used for large concave gratings, whereby the slit, grating and plate holder lie in the Rowland circle, and the photographic plates lie along a large portion of the circle. In this way, a...

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...

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 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.

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...

A phage, short for bacteriophage, is a type of virus that infects and replicates within bacteria. Phages are composed of genetic material (either DNA or RNA) surrounded by a protein coat. They are...

The use of a reflective device, which can be fashioned from a variety of materials including gases, solids, dyes, aerosols, semiconductor crystals and plasmas, to replicate a laser beam by reversing...

With respect to a traveling plane wave at a known frequency, the space rate of decrease of phase of a field component in the direction of propagation, measured in radians per unit length.

Phase contrast microscopy is an optical microscopy technique that enhances the contrast of transparent and colorless specimens, making it possible to visualize fine details and internal structures...

A technique used to generate a phase shift between reference and sample light beams. The phase shift can be performed through the use of a mirror that is moved along the optic axis by a piezoelectric...

The propagation or hindrance of waves reaching each aperture of the interferometer because of atmospheric turbulence.

A method of coding information in a communications system where the shift in the phase of an electromagnetic wave represents a particular bit or character.

In biology, particularly genetics and evolutionary biology, the phenotype refers to the observable characteristics or traits of an organism, resulting from the interaction of its genetic makeup...

The term applied to the geometrical structure of radiometry or of the propagation of any quantity that is conversed and that travels in straight lines at velocities characteristic of the medium.

A phonon is a quantum of vibrational energy associated with the periodic motion of atoms or molecules in a crystalline lattice. In simpler terms, phonons are quanta of lattice vibrations in a solid...

A process used in pyrometry and photothermometry to create a photographic record of a surface's temperature gradients. Essentially, it involves the exposure of a glowing phosphorescent surface to the...

Abbreviated PAI. An imaging modality with a hybrid technique based on the acoustic detection of optical absorption from endogenous chromophores or exogenous contrast agents. Light is absorbed by the...

A method for obtaining the optical absorption spectra of solids, semisolids, liquids and gases. PAS is inherently insensitive to reflection or scattering from the sample, analyzes opaque samples and...

Photobleaching is a phenomenon in which the fluorescence of a fluorophore (a fluorescent molecule or dye) is permanently reduced or eliminated upon prolonged exposure to light. This process occurs...

Photocathodes are specialized materials or surfaces that exhibit the photoelectric effect, wherein the absorption of photons leads to the emission of electrons. When photons with sufficient energy...

A method of producing disks for erasable optical data storage. Information is recorded by a laser beam that generates pits on the surface of the disk while it is being cryogenically cooled. Erasure...

Photochromic refers to a property exhibited by certain materials, typically organic compounds or dyes, which undergo reversible changes in color when exposed to light. Specifically, photochromic...

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...

A photodetector, also known as a photosensor or photodiode, is a device that detects and converts light into an electrical signal. Photodetectors are widely used in various applications, ranging from...

A spectroscopic process that detects and analyzes the discharge from an extrinsic surface with less than bandgap light. This method may determine the extrinsic surface-state energy levels of a...

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...

Photoelastic equipment and supplies refer to instruments and materials used in photoelasticity, a technique used to analyze stress distribution and behavior in materials. photoelastic equipment...

Also known as light beating. The mixing of two narrowband optical components to produce an AC component in the photocurrent at the optical difference frequency.

Surface analysis by means of photon induced electron emission. PEM methods provide high lateral resolution of the observed sample.For surface material sciences PEM allows the investigation of...

The use of photographic emulsions to detect and determine the amounts of ionizing radiation, such as x-rays and gamma rays, in an area. This is accomplished by exposing the emulsion to the radiation...

The ionization that occurs in gas affected by the action of radiation quanta.

Photolithography is a key process in the manufacturing of semiconductor devices, integrated circuits, and microelectromechanical systems (MEMS). It is a photomechanical process used to transfer...

A technique used for noncontact inspection of semiconductor wafers. The material is illuminated by an excitation source that stimulates photoluminescence; the resulting spectrum is analyzed, yielding...

Photoluminescence is a phenomenon in which a material absorbs photons (light) at one wavelength and then re-emits photons at a longer wavelength. This process occurs when electrons in the material...

A photomultiplier tube (PMT) is a highly sensitive vacuum tube that detects and amplifies low levels of light. It is widely used in various applications where high sensitivity, fast response times,...