Photonics Dictionary

A substrate refers to a material or surface upon which another material or process is applied or deposited. In various fields, such as electronics, biology, chemistry, and manufacturing, the term...

Supercontinuum refers to a broad spectrum of light that spans a wide range of wavelengths, typically from the visible to the near-infrared or even mid-infrared regions of the electromagnetic...

Directional and coherent radiation pulses that result from an ensemble of coherently prepared states in an optical medium.

Waves that propagate along the interface between two different media without radiation with exponentially decaying evanescent fields on both sides.

A wave that is guided by the interface between two different media or by a refractive index gradient in the medium. The field components of the wave may exist (in principle) throughout space, even to...

Surface-enhanced Raman spectroscopy (SERS) is an analytical technique that combines the principles of Raman spectroscopy with the enhancement provided by nanostructured metallic surfaces. Raman...

In a laser, the voltage necessary to sustain a constant operating current, somewhat less than that needed for start-up.

A swept-source laser, also known as a wavelength-swept laser, is a type of laser that rapidly and continuously changes its emission wavelength over time. This continuous wavelength tuning is achieved...

A telescope lens is a primary optical component of a telescope system that gathers and focuses light to form an image. It is typically a curved, transparent piece of glass or other optical material...

The base used to hold an astronomical telescope. It may be either altazimuth, with horizontal and vertical axes of rotation, or equatorial, with one axis parallel to the Earth's axis of rotation and...

A characteristic of laser output, calculated by dividing the speed of light by the linewidth of the laser beam. The temporal coherence length of different lasers thus varies from a few centimeters to...

A technique used to suppress extreme noise amplification during digital image reconstruction that relies on smoothing and differentiation of the data by simplified least squared procedures.

A synonym for spatial coherence. See spatially coherent radiation.

A transparent block shaped accurately to reverse curvatures of the components it is used to test. By contacting an accurately finished negative lens shape with a newly made positive, the conformity...

A refrigeration method based on the Peltier effect. When an electric current passes through a thermocouple of two dissimilar metals joined in two places, heat is absorbed at the cold junction and...

Also known as analog thermogram. The resultant photograph, illustrating, in tones ranging from black to white, the spatial relationship of the infrared radiation temperatures of the different details...

Thermography is a technique that involves the use of an infrared imaging device, called a thermal camera or infrared camera, to detect and visualize the infrared radiation emitted by objects. This...

Thermophotovoltaic (TPV) refers to a technology that converts heat energy into electricity using the principles of thermophotovoltaics. In a thermophotovoltaic system, thermal radiation from a heat...

A thin layer of a substance deposited on an insulating base in a vacuum by a microelectronic process. Thin films are most commonly used for antireflection, achromatic beamsplitters, color filters,...

A transparent dielectric film, bounded by material of a lower index of refraction, capable of guiding light.

In laser damage testing, the exposure of many sites of a sample to different intensities of laser irradiation to discover the point at which the laser induces failure of the material.

1. Voltage at which a PN junction begins to pass a current. 2. In a solid-state lamp, the voltage at which light is first emitted.

The process or device by which more than one signal can be sent over a single channel by using different time intervals for the different signals. This may be done by varying the pulse duration,...

A laser fitted with up to eight optical fibers that transmit the energy to different workstations in turn.

A variation of tomography in which several photographs of a patient are taken at different angles, and back-projection of the resulting radiographs produces light distribution in a chosen...

Topological photonics is a branch of physics and optics that explores the application of topological concepts to the behavior of light in photonic systems. Drawing inspiration from the field of...

Topology is a branch of mathematics that focuses on the properties of space that are preserved under continuous deformations, such as stretching, crumpling, and bending, but not tearing or gluing....

A surface that is swept out by revolving a circle about an axis that lies in the plane of the circle but that does not intersect its center. The result is a surface having different curvatures in...

A transparent diffraction grating that serves to transmit light.

An image affixed to a transparent photographic film or plate by photographic, printing or chemical methods. It may be viewed by transmitted light.

Multiple scattering method used in biological analysis in which approximations yield simple, explicit solutions, at least for slab geometry. The approximations are usually differential equations...

A Pockels cell in which electrical current is applied in a direction orthogonally to that of the light beam.

In the context of optics and lasers, a transverse mode refers to a specific spatial pattern of the electric field within the cross-section of a laser beam. These modes represent the different...

The method for measuring the index profile of an optical fiber or preform by illuminating it coherently and transversely to its axis, and examining the far-field radiation pattern.

Also known as TEA laser. A coherent optical source with a wide wavelength range in the infrared, visible and ultraviolet that uses an electrical discharge transverse to (across) the optical axis to...

Oscillator device composed of a semiconducting diode in a coaxial resonating cavity. When the biasing current is applied to the diode, high-frequency waves are emitted into the cavity where they are...

A traveling wave tube (TWT) containing a photocathode and window that, receiving a laser beam, produces a modified photoelectric current that is accelerated and propagated into its helical frame.

The size of the field of view in the object space of an optical system as differentiated from that in the image space (apparent field).

An evacuated bulb containing a tungsten filament that is heated by passing an electric current through it. In domestic light bulbs the inside of the bulb is frosted to soften shadows. In projection...

Ultrasonic refers to sound waves with frequencies higher than the upper audible limit of human hearing, typically above 20,000 Hz. These waves are termed ultrasonic because they are beyond the range...

Ultraviolet (UV) fiber optics refers to optical fibers that are designed and optimized for the transmission of ultraviolet light, which is electromagnetic radiation with wavelengths shorter than...

A type of lamp that emits a high quantity of ultraviolet radiation. This may be an arc lamp encased in a bulb of a glass that is transparent to ultraviolet rays.

A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz, calcium fluoride, lithium fluoride or some other material transparent to ultraviolet radiation, as glass...