Photonics Dictionary

In the region of a Gaussian beam focus by a diffraction-limited lens, it is the axial distance from the point of minimum beam waist (Wo) to the point where the beam diameter has increased to .

Rayleigh scattering is a phenomenon that occurs when light waves interact with particles or molecules that are much smaller than the wavelength of the light. It is named after the British scientist...

Reactive evaporation refers to a process in thin-film deposition where a material is deposited onto a substrate through evaporation, and chemical reactions take place during or after the evaporation...

A read-out integrated circuit (ROIC) is an electronic device used in imaging systems, particularly in infrared (IR) and other sensing technologies. It is designed to interface with an array of...

A reagent is a substance or compound that is used in a chemical reaction to bring about a specific transformation or to detect the presence or absence of another substance. Reagents are employed in...

The ability of a vision system to interpret an image in a short enough time to keep pace with most operations.

A nonhomogeneity of index in flat glass that is in the form of an approximately plane layer.

A photodetector mounted in the same package as a laser diode that is positioned to monitor the output from the rear facet of the diode.

With respect to photography, the law stating that the optical density of an exposed emulsion with standard development is a function of just the irradiance and the exposure times.

Recombinase polymerase amplification (RPA) is a molecular biology technique used to rapidly amplify specific DNA or RNA sequences under isothermal conditions, meaning it does not require the...

The radiation emitted in semiconductors when electrons in the conduction band recombine with holes in the valence band. If population inversion occurs between portions of the valence and conduction...

A reconfigurable optical add-drop multiplexer (ROADM) is a key component in wavelength-division multiplexing (WDM) optical communication networks. It allows for flexible and dynamic routing of...

An image that appears when a hologram is illuminated by a suitable light source, generally a laser beam.

Holographic quantity expressed as the ratio of the reconstructed first-order image to that of the incident reconstructing beam.

The coherent wave used to play back a recorded hologram. It is identical to the reference wave used in the generation of the original hologram; part of it is diffracted by the recording medium and...

A technique used in photogrammetry to ensure parallelism during projection printing. Failure to do this will change a rectangular image on a negative into a trapezoidal image on the print.

In holography, the beam of light that is directed from the beamsplitter to the recording medium, where it interferes with the object beam to generate the hologram.

The surface of an optical fiber that is used as a reference when joining optical fibers. Although the outermost cladding is usually used, the core cladding surface is also a common reference point.

Reflectance confocal microscopy (RCM) is a non-invasive imaging technique that allows for high-resolution, in vivo imaging of biological tissues at the cellular level. It is particularly useful in...

An instrument that spectrally analyzes the flux reflected from a material. The reflected flux may be total, diffuse or specular. Often the instrument measures the reflectance factor instead of the...

A photographic method used to obtain an image of a subject by means of its reflectance of incident ultraviolet radiation. An ultraviolet source is used to irradiate the subject, while the reflected...

Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface; diffuse, from a rough surface or from within the specimen; or mixed, a...

Parametric measurement for elliptical fiber and cable expressed as a ratio of the two-directional flow of power through the cable at any chosen point.

A hologram that is illuminated by a source from the viewer's side.

Reflectance spectroscopy is a technique used to analyze the reflective properties of materials across various wavelengths of the electromagnetic spectrum. By measuring the reflectance of light from a...

The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of radiation. It implies the capability of bouncing back or redirecting...

The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high numerical aperture cone and measuring the change in power of refracted...

A measure of the relative difference in refractive index between two optical materials. Most commonly used in fiber optics where the refractive index contrast, D, is given as follows: where n1 equals...

A closely spaced series of well-known chemicals having a refractive index lying between 1.33 for water and 1.95 for a solution of phosphorus in carbon disulfide. They are used to identify powdered...

The method used to determine the refractive index of a given substance.

A plot showing how the response (ability to detect a signal) varies with wavelength. D(l).

A form of lens assembly used in a projection system to maximize efficiency and assure uniform illumination of the object being projected.

A lens or lens system used to transfer a real image from one point within an optical system to another, with or without magnifying it.

A display device, such as a cathode-ray tube, that is located at some distance from the source generating the displayed information.

Remote inspection refers to the process of inspecting, evaluating, or monitoring assets, equipment, infrastructure, or systems from a distance, typically using remote sensing technologies and...

Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on Earth's surface is gathered from a distance, typically using sensors onboard...

A pulsed laser that emits a recurring pulsed output. Frequency of the pulses emitted is known as pulsed recurrence frequency (PRF). When the PRF or duty cycle is very high, repetitively pulsed lasers...

Ratio between map or photo linear distance and the actual ground dimensions represented.

A chart on paper or glass containing a series of sets of lines at progressively smaller spacing and used to ascertain the limiting number of lines per millimeter that an optical system is capable of...

Resonance can be defined in various contexts, including physics, chemistry, and music. Here are definitions for resonance in a few different fields: Physics: In physics, resonance refers to the...

That radiation emitted by an atom or molecule that has the same frequency as that of an incident particle; e.g., a photon. It generally involves a transition to the lowest energy level of the atom or...