Photonics Dictionary: S

An instrument consisting essentially of a photoelectric cell filtered to respond to a specified wavelength region, an amplifier of sufficient gain to provide power enough to control movement of a...

Correction of an optical system at four separate wavelengths. This correction, longitudinal and lateral, is possible with the help of three selected special glasses.

A metal, alloy or compound that loses its electrical resistance at temperatures below a certain transition temperature referred to as Tc. High-temperature superconductors occur near 130 K, while...

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...

Observed phenomenon in laser pulses in which a large number of excited electrons are created and in which multiphoton processes have produced seed electrons, and excited neutral atoms are...

The process in which the normal rate of fluorescent emission from a substance is enhanced by virtue of the optical gain of the medium; i.e., energy is lost not only by spontaneous emission but also...

An image of an object that appears above the object's true position as the result of abnormal refraction of the image rays by the atmosphere.

Superluminal transmission refers to the hypothetical process of transmitting information faster than the speed of light, which is commonly denoted as superluminal or faster-than-light (FTL)...

An emitter based on stimulated emission with amplification but insufficient feedback for oscillation to build up.

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

A reflector having a surface that has been superpolished to reduce residual sleeks and scratches and microroughness so that its scatter coefficient is low. Its surface is said to have a low-scatter...

Superresolution refers to the enhancement or improvement of the spatial resolution beyond the conventional limits imposed by the diffraction of light. In the context of imaging, it is a set of...

A liquid crystal display using the material in its supertwisted nematic phase; the birefringence of the liquid crystal results in a characteristic yellow or blue color, unless corrected.

A form of liquid crystal in which the 90° twist of the twisted nematic phase has been increased to 180° or more, resulting in higher contrast and a wider viewer angle in the display.

A meniscus that is often fitted before a camera lens to permit focusing on near objects.

A mass spectrometer used to detect ions formed by photo- and charge-exchange ionization of gases, such as those in the lunar atmosphere.

1. In optics, one of the exterior faces of an optical element. 2. The process of grinding or generating the face of an optical element.

An acoustic wave that propagates along the surface of a solid and decays exponentially with substrate depth. Also called a Rayleigh wave, it has both longitudinal and transverse (shear) components....

(SALI) A type of spectroscopy in which neutral atoms or molecules are ionized by an excimer laser beam and then measured by a time-of-flight mass spectrometer.

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

The departure of an optical surface from its required tolerance or figure.

A large table with an accurately designed plane surface used to test other surfaces, or to provide a true surface for accurately locating a testing fixture. Most commonly made of granite.

A representation of the shape of a surface, including any roughness or other irregularities. The profile can be generated by direct measurements, as by a stylus, or by remote measurement, as by an...

The specification of allowable flaws in a surface by comparison to reference standards of quality. Two graded sets of surface quality standards are employed. The first denotes defects of a long...

The standards of MIL-O-13830 set by the US government relative to tolerable surface scratches and other such defects in an optical system. A series of standard glass plates that have been...

Also known as Fresnel reflection. That portion of the incident radiation that is reflected from the surface of a refractive material. It is a function of the refractive index of the material. At...

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...

A semiconductor laser diode that emits light perpendicular to the active region. The output radiation is taken through the surface as opposed to through a cleaved mirror.

A technique of optical storage whereby information is encoded by molecular alterations in the interaction between the optical layer and the substrate.

Surface-enhanced Raman scattering (SERS) is a powerful analytical technique that enhances the Raman scattering signal of molecules adsorbed on or near certain nanostructured surfaces. Raman...

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...

A surface-mount device (SMD) is an electronic component that is mounted directly onto the surface of a printed circuit board (PCB) rather than being inserted into holes drilled in the board (as with...

A term that describes both the color and intensity of the immediate environment of the object or image being viewed.

Instruments used for measuring angles and occasionally lengths on the ground. The principal surveying instruments are the level, the stadia telescope, the transit and the theodolite. Laser...

A small telescope mounted on a tripod and free to rotate about a vertical axis. A spirit level is mounted over the telescope and adjusted so that when the bubble is central, the telescope axis is...

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

The material removed during diamond machining of glass components.

Swept-source optical coherence tomography is an imaging technique used in medical diagnostics, particularly in ophthalmology, to visualize and analyze the internal structures of biological tissues,...

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 positive after-image that is maintained for a minute or more.

The length of the oscillation of a grinding or polishing lap.

A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the other. The lens sets are arranged symmetrically on either side of the...

A synapse is a specialized junction between two neurons (nerve cells) or between a neuron and a target cell (such as a muscle or gland cell). It is the fundamental functional unit of communication in...

Abbreviation of "synchronization.'' In television, the timing signals used to drive the scanning process. Horizontal sync triggers the retracing of the raster line beginning at the left-hand...

A detector sensitive only to signals close to or at a particular frequency that is the same as the frequency of a control signal applied independently. The synchronous detector also is...

A standard for fiber optic telecommunications interfaces, with a 1300-nm data link operating over single-mode fiber at data rates of 52, 155 and 622 Mb/s.