Photonics Dictionary: S

An aberration that remains after primary color is corrected. Primary color causes the back focus of a lens to vary with wavelength; for example, blue light comes to focus closer to the lens than...

A self-interference effect that generates random patterns; secondary speckle pattern (SSP) typically occurs in diffuse reflections of a laser on paper, white paint or rough surfaces. By tracking both...

An arrangement of optical fibers in a bundle whereby the geometric configuration of the input end differs from that of the output end without changing the total area; for example, a circular bundle...

Characteristic of dissimilar metals in thermoelectric solar cells whereby separate junctions exhibiting distinct temperatures transform incident voltage into a current.

1. In glass, a solid inclusion having a small diameter. 2. A particular, single crystal that, after undergoing the Czochralski method, evolves into large single crystals.

In multifocal spectacles, a term used to denote glass with a high refractive index that has been fused to the blank and ground to a curvature, resulting in added power.

Seidel aberrations refer to a set of monochromatic aberrations in optical systems, named after the German mathematician and physicist Ludwig von Seidel. These aberrations describe deviations from...

Selective laser melting (SLM) is an additive manufacturing (AM) or 3D printing technology that belongs to the powder bed fusion category. SLM is primarily used for metal additive manufacturing, where...

The reflection in different amounts as a function of wavelength, as a result of absorption and scattering, leading to color effects if occurring in the visible wavelength region.

Transmission in different amounts as a function of wavelength, as a result of absorption and scattering, leading to color effects if occurring in the visible wavelength region.

Self-phase modulation (SPM) is a nonlinear optical phenomenon that occurs when an intense laser beam passes through a medium, causing a change in the phase of the light due to its interaction with...

An equation that uses the wavelength of light passing through a medium, along with a set of coefficients, to calculate the medium's index of refraction. The coefficients, called Sellmeier...

A semiconductor is a type of material that has electrical conductivity between that of a conductor and an insulator. In other words, semiconductors have properties that are intermediate between...

A formed piece of glass, one surface of which has been ground and polished to the required curvatures.

A photocathode that receives radiation from one side and emits a photoelectric current from the opposite side.

An instrument for determining the sensitivity of a photographic film to light. The film is given either a stepped exposure or a continuously varied exposure; after processing, the density is measured...

An avalanche photodiode in which the light-absorbing area is a low-bandgap material and the PN junction is placed in an area of high-bandgap material, reducing dark current and increasing gain.

With respect to television, the transmission of the signals that originate from variously colored parts of an image in a particular sequential order.

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 type of motor that acts as the control element in a servomechanism. It is powered by an amplifier circuit and drives the load with linear or rotary motion.

A handheld navigational instrument used to measure the elevation angle of celestial bodies such as the sun. An image of the sun is viewed through a small telescope via two plane mirrors so that any...

The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system. It is widely used in adaptive optics systems to correct distortions and...

A term used to denote a concave surface having too long a radius of curvature. That is, its negative power is too small or low.

A term used to describe a convex surface having too short a radius of curvature. To correct this condition, material is cut from the outer portion of the polishing tool.

A function of the intensity distribution in an image aberrated by a quadratic curvature wavefront distortion.

Image distortion that occurs when the axes of the original image are not perpendicular in the resulting image, making the resulting image appear slanted. Shear can be caused by movement of the...

A sheet of plastic material containing microscopic crystals of herapathite or some other similar substance that transmits light polarized in one direction, but absorbs light polarized in a...

Short wavelength infrared (SWIR) refers to the portion of the infrared spectrum that encompasses wavelengths roughly between 1,000 and 3,000 nanometers (nm). In the electromagnetic spectrum, infrared...

A compact high-pressure light source in which an electrical discharge between electrodes spaced no more than 12 mm apart occurs in a xenon or other gas medium, providing a visible light resembling a...

An electronic flash tube in which the flash recurs at a frequency extending to many thousands per second. A stroboscopic light source is a short-flash light source.

A device used to measure the opening time of a shutter. The most common devices depend on the charging or discharging of an electrical condenser, or on the production of a curve of open area against...

The electric conductance of a conductor in which a current of 1 ampere is produced by an electric potential difference of 1 volt.

A convention that defines specific dimensions of an optical system, such as the image distance or radius of curvature of a lens or mirror, as negative or positive to facilitate calculations based on...

Calculation of peak and average transmission power at a given point along an optical fiber or cable.

Noise generated in the flow of current in the photomultiplier, produced by the intentional or controlled application of optical power to the photocathode.

Silicon carbide (SiC) light-emitting diodes (LEDs) are semiconductor devices that emit light when an electric current is applied to them. These LEDs are made using silicon carbide as the...

A silicon photodiode is a semiconductor device that converts light into an electrical current. It is a type of photodetector specifically designed for detecting and measuring light intensity. Silicon...

The ability of an electrical current to destroy superconductivity by means of the magnetic field generated by the current. The temperature of the material is not raised, and the effect is identical...

Bar pattern represented as a sine curve in which the light distribution varies in one direction.

A single-photon avalanche diode (SPAD) is a specialized type of photodetector designed to detect extremely weak optical signals, down to the level of single photons. SPADs are widely used in...

The method for measuring the index profile of an optical fiber by preparing a thin sample that has its faces perpendicular to the axis of the fiber, and measuring its index profile by interferometry.

The process of making an abrupt break in a spherical surface on a spectacle lens so that a new center of curvature is set for a portion of the lens. This has the effect of adding a prism to that...

A television system that uses a slow rate of horizontal scanning to increase its reproduction and transmittance accuracy of printed matter, photographs and illustrations.