Definitions

Quantum efficiency (QE) is a measure of the effectiveness with which a device or system, typically in the context of photonics or electronics, converts incoming photons (light) into a useful output...

Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become correlated to such an extent that the state of one particle instantly influences the state of the...

Quantum key distribution (QKD) is a method of secure communication that utilizes principles from quantum mechanics to establish a shared secret key between two parties, typically referred to as Alice...

The science of all complex elements of atomic and molecular spectra, and the interaction of radiation and matter.

Noise generated within an optical communications system link that has both internal (dark current) and external (background noise, or noise in signal) components.

The area of optics in which quantum theory is used to describe light in discrete units or "quanta" of energy known as photons. First observed by Albert Einstein's photoelectric effect, this particle...

A quantum repeater is a crucial component in quantum communication networks, designed to extend the range over which quantum information can be transmitted. Quantum information, typically carried by...

Quantum sensing refers to a class of sensing technologies that leverage principles from quantum mechanics to enhance the precision and sensitivity of measurements. Traditional sensors operate based...

A quantum well is a structure in quantum mechanics that confines particles, such as electrons or holes, in one spatial dimension. This confinement leads to quantized energy levels, creating a...

A narrow channel created by cleaving a crystal made of alternating layers of gallium arsenide and aluminum gallium arsenide, and adding additional layers on the cleaved end face, at right angles to...

Quantum-enhanced metrology refers to the use of quantum mechanics principles and techniques to enhance the precision and sensitivity of measurements in metrology—the science of measurement....

Operation in which the minimum detectable signal is set because of variations in the average signal current; e.g., quantum noise.

A plate made of a double-refracting crystal having such a density that a phase difference of one-quarter cycle is formed between the ordinary and extraordinary elements of light passing through.

See crystal quartz; fused quartz.

A lamp with a quartz envelope that transmits radiation generally rich in the ultraviolet.

A crystalline-quartz plate designed according to specifications but having its two major faces parallel.

A spectrograph used to detect radiation in the range of the ultraviolet in the electromagnetic spectrum. It is made up of quartz because that material, unlike regular glass, is not opaque to the...

A contraction of quasi stellar. An astronomical object that appears to be a star but has a different, larger redshift.

A type of laser diode that operates at long pulsewidths.

A laser that generates a succession of pulses at a high enough repetition rate to appear continuous. The pump source is switched on for short intervals, nominally equal to the lifetime of the...

The transform defining that, if a reference beam is a divergent spherical wavefront, then the reconstructed image will be the equivalent of the near-field diffraction pattern of the object. Also...

The first nonlinear theory in plasma physics that details the time and space evolution of plasma wave instability from a microscopic vantage point and provides an outline of the plasma in terms of...

Single wavelength source with a larger linewidth often containing multiple longitudinal modes.

Having properties resembling those of light- waves; e.g., the propagation of waves in the television spectrum.

A quasiparticle is an emergent phenomenon that occurs in many-body systems, particularly in condensed matter physics, where the collective behavior of a large number of interacting particles can be...

Made up of four elements; for instance, gadolinium, scandium, gallium and garnet (GSGG).

A qubit, short for quantum bit, is the fundamental unit of information in quantum computing and quantum information processing. Unlike classical bits, which can exist in one of two states (0 or 1),...

In the dye laser, the molecule that takes out energy from the triplet state during collisions between the dye and quencher to achieve long-pulse emission.

The inhibition or elimination of one process by another process. The stimulated emission of a laser oscillator can be quenched by a pulse of radiation of the same frequency traversing the oscillator...

The time interval of no activity occurring between each pulse during transmission.

Rabi oscillations are a fundamental phenomenon in quantum mechanics that describe the periodic and reversible exchange of energy between two quantum states when subjected to an oscillating external...

Inactive optically, but having the capacity for resolution into forms of opposed optical activity. The term is derived from racemic acid, an optically inactive, tartaric acid.

A unit of energy absorbed from ionizing radiation, equal to 100 ergs per gram of irradiated material.

The spontaneous visual presentation of radar information by electronic traces on a cathode-ray tube.

The analysis of the photographs taken from the radar display of a survey aircraft and used when recording terrain that is obscured by clouds.

An acronym for radioactive detection, identification and computation. The term refers to the detection and measurement of the intensity of emitted nuclear radiation.

The astigmatism in a lens system that results when light enters the system at an oblique angle.

An alteration in magnification from the center of the field to any point in the field, measured in a radial direction from the center of the field. Some radial distortion is inherent in most optical...

A statistical analysis of facts obtained when the intensity of x-ray diffraction is calculated at different angles. In this way, the interatomic distances of gases and liquids can be deduced, with...

In gradient index optics, a gradient profile in which the index varies in a direction perpendicular to the optical axis. Radial gradient lenses can focus light even when the lens surfaces are flat,...

A grating in which the wires or rods are set radially within a circular structure.

The deviation from the ideal case where a circular variable filter is located at a given wavelength along a radial line (or constant angle of rotation) regardless of the distance from the center of...

The velocity from object to observer, directed along the line of sight.

A reflecting optic whose reflectivity is a function of the radial distance from the optic axis; can be used to convert a Gaussian beam to one of uniform cross section.

The unit angle, within an arc of a circle, equal to the radius of the circle (180/p°, numerically).

Radiant power per unit source area per unit solid angle. Usually it is expressed in watts/m2/steradian.

Ratio of the radiance of the specimen to that of a perfect reflecting or transmitting diffuser identically irradiated.

Pertaining to electromagnetic radiation, with the contributions at all wavelengths of interest weighted equally.