Photonics Dictionary: P

The transformation of incident radiant energy into a photoelectric emission current.

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...

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 microscope that has an annular stop in the lower focal plane of the condenser, and a quarter-wave retarding and absorbing ring in the upper focal plane of the objective that just fills the image of...

Periodic interruptions of a light beam incident on an absorbing medium that produce heat, expansion and acoustic wave generation. Since the amplitude of this wave is proportional to the absorbed...

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.

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...

The term photochemical pertains to chemical processes or reactions that are initiated or influenced by the absorption of light. Photochemical reactions involve the interaction of light, often in the...

A chemical compound that exhibits a reversible change in its absorption spectrum upon irradiation with given wavelengths of light.

The discrepancy between the absolute luminance threshold and the photochromatic threshold.

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...

The reversible change in the absorption spectrum of certain compounds upon irradiation with a given wavelength of light.

The alteration of electric conductivity produced by the absorption of varying amounts of radiation composed of photons.

A film of material that exhibits varying conductivity based upon its absorption of varying amounts of photon radiation.

The conductivity increase exhibited by some nonmetallic materials, resulting from the free carriers generated when photon energy is absorbed in electronic transitions. The rate at which free carriers...

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...

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...

The constant that, multiplied by the frequency of the radiation-producing emission of photoelectrons, determines the amount of voltage each photoelectron absorbs.

The emission of an electron from a surface that occurs when a photon impinges upon the surface and is absorbed. This effect is the means by which photons may be detected.

That property of a material that determines its ability to release electrons when absorbing photons.

Photoimmunotherapy (PIT) is a medical treatment approach that combines elements of phototherapy and immunotherapy to target and treat specific cells or tissues in the body. The key components of this...

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,...

Photonic crystals are artificial structures or materials designed to manipulate and control the flow of light in a manner analogous to how semiconductors control the flow of electrons. Photonic...

A photonic cavity, also known as an optical cavity, is a structure that confines electromagnetic radiation within a certain region or volume. It is typically composed of materials with different...

Photoplethysmography (PPG) is a non-invasive optical technique used to detect changes in blood volume in tissues. It measures variations in light absorption caused by the pulsatile nature of blood...

Participates in a reaction only in the presence of light and radiant energy. Besides 3D printing, photoreactive agents also have an application in light therapy. By absorbing light, photoreactive...

The surface from which electrons are ejected by the incidence and absorption of photons.

Photosynthetically active radiation (PAR) is the 400- to 700-nm region (visible light) of the electromagnetic spectrum that is absorbed and used by the plant for photosynthesis. Also referred to as...

The cause of some forms of laser injury in which tissue absorbs incident laser light and experiences a damaging rise in temperature. The severity of the damage is dependent on the rate of energy...

Phototoxicity refers to the harmful effects caused by exposure to light, particularly intense or ultraviolet (UV) light, on living cells or organisms. This phenomenon is often associated with the...

A broadband, visible picosecond probe pulse capable of measuring an entire absorption spectrum in one shot.

A PIN photodiode is a type of photodetector or semiconductor device used to convert light signals into electrical signals. The name "PIN" is derived from the arrangement of the three semiconductor...

Plasmonics is a field of science and technology that focuses on the interaction between electromagnetic radiation and free electrons in a metal or semiconductor at the nanoscale. Specifically,...

The property exhibited by certain birefringent crystals in which the degree with which they transmit polarized light is different, depending on whether the ray is ordinary or extraordinary. An...

A mixture of ionized gas and metal vapor generated by impingement of the laser beam onto a material being welded or a weld joint. The plume causes absorption and/or scattering of the incident laser...

Discharge that results when a doped semiconductor crystal with a PN junction is charged with a low-voltage direct current. The dual process depends on excitation caused by electrical energy...

A device used in solar systems to direct mirror-reflected sunlight to a heat absorber and heat-driven engine, which turns a generator to produce electricity.

A subsurface imaging technique based upon the polarization of light reflected off an object. The polarization of reflected light gives information about the object's absorption properties that...

The condition in which there are more atomic systems in the upper of two energy levels than in the lower, so stimulated emission will predominate over stimulated absorption. This condition may be...

Acronym for profile resolution obtained by excitation. In its simplest form, probe involves the overlap of two counter-propagating laser pulses of appropriate wavelength, such that one pulse...