Photonics Dictionary: P

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.

Oscillation in rod and disc amplifiers that critically limits the achievable energy storage.

Totally coherent radiation is produced by a purely monochromatic point source. In the real world the energy will have a limited bandwidth and the point source will subtend some angle resulting in...

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 wave of radiant energy in which each point of the wave is repeatedly displaced at equal time intervals.

Phase matching is a crucial concept in the field of optics, particularly in nonlinear optics and the generation of coherent light. It refers to the condition where the phases of two or more waves,...

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 chemical substance that exhibits fluorescence when excited by ultraviolet radiation, x-rays or an electron beam. The amount of visible light is proportional to the amount of excitation energy. If...

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...

The responsivity of a photocathode to luminous energy equal to the ratio of the photoelectric emission to the incident luminous flux.

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...

An instrument used to detect and measure radiant energy by the formation of a chemical reaction.

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 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...

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

A system that consists of a spectrophotometer with a photoelectric detector for measurement of radiant energy.

The use of photographic recording equipment to measure radiant energy. With this procedure, many measurements of radiant energy can be recorded simultaneously and permanently.

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,...

A quantum of electromagnetic energy of a single mode; i.e., a single wavelength, direction and polarization. As a unit of energy, each photon equals hn, h being Planck's constant and n, the frequency...

The property exhibited by a substance having electrical conductivity that decreases as the intensity of the incident visible radiant energy increases.

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and...

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...

That property of a material indicating that it will react when exposed to light energy.

A document-transmitting process that uses a cylinder that rotates the document to be scanned and detected by a photoelectric cell. The cell transforms the light into electrical energy that may be...

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 phototransistor is a type of semiconductor device that converts light energy into electrical signals. Similar to a regular transistor, it consists of a semiconductor material (such as silicon) with...

A photovoltaic cell, commonly known as a solar cell, is a semiconductor device that directly converts light energy into electrical energy through the photovoltaic effect. The photovoltaic effect is...

Photovoltaic (PV) refers to a technology that converts sunlight directly into electricity using semiconductors. The term "photovoltaic" is derived from the words "photo," meaning light, and...

Piezoelectric transducers are devices that utilize the piezoelectric effect to convert electrical energy into mechanical vibrations or vice versa. The piezoelectric effect is a property exhibited by...

Piezoelectricity is a property exhibited by certain materials in which they generate an electric charge in response to mechanical stress or deformation, and conversely, undergo mechanical deformation...

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...

The universal constant h that has a value of 6.6260693 x 10-34 Js. A quantum of energy is equal to the product of the frequency of the radiation and Planck's constant.

A fundamental law of quantum theory which states that the discrete quanta of energy transfers associated with electromagnetic radiation are proportional to the frequency of the radiation.

A plasma accelerator is a type of particle accelerator that uses electric fields and magnetic fields to accelerate charged particles, typically electrons or ions, by exploiting the motion of charged...

Plasmon ion-assisted deposition (PIAD) is a technique used in thin-film deposition processes, particularly in the production of optical coatings. This method combines two key processes: plasmon...

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,...

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 to detect radiant energy by means of the thermal expansion of gas.

The measurement of the rotation of the plane of polarization of radiant energy, usually through the use of a polarimeter.

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...

For a pulsed laser, the product of the energy per pulse (joule) and the pulse frequency (hertz); expressed in watts.