Photonics Dictionary: S

1. The decrease of the absorption (or gain) coefficient of a medium near some transition frequency when the power of the incident radiation near that frequency exceeds a certain value. As long as the...

Scanning electron microscopy (SEM) is an advanced imaging technique used in microscopy to obtain high-resolution, three-dimensional images of the surfaces of solid specimens. SEM achieves this by...

An instrument used to determine the absolute or relative scatter levels of optical surfaces.

Oscilloscope electronic circuit that produces an output pulse whose pulse width is determined by the time that the output voltage exceeds a specified level.

1. The variation in intensity of a light beam as it travels through the atmosphere. 2. In radiation physics, a light flash formed by an ionizing event in a phosphor; a flash formed when rapidly...

A scintillation detector is a radiation detection device that utilizes scintillation crystals to detect and measure ionizing radiation, such as gamma rays, x-rays, or charged particles. It consists...

Vision by means of retinal rods; vision of the dark-adapted eye. In scotopic vision, the level of luminance is so low that the retinal cones are not stimulated, and there is no color vision.

An instrument that uses an image intensifier to aid in the viewing of subjects in low-light-level environments.

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 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...

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

The process, used with a positive photoresist, in which the photoresist is immersed in developing chemicals while being exposed to the optical pattern. The newly exposed surface is continuously...

Single-molecule Förster resonance energy transfer (smFRET) is a specialized technique in biophysics and molecular biology used to study the distances and dynamic interactions between two...

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...

An instrument used for viewing in low levels of illumination by means of infrared radiation. A high-aperture lens forms an image of distant objects on the photocathode of an infrared-sensitive image...

Term applied to radiation composed of particles or photons that will not easily penetrate a material because of their low energy levels.

A solar simulator is a device used to replicate the spectrum and intensity of sunlight in a controlled environment for testing and research purposes. Solar simulators are employed in various...

A solid-state laser is a type of laser that uses a solid gain medium (as opposed to a liquid or gas) to produce coherent light. The term "solid-state" refers to the fact that the active medium, where...

Spatial resolution refers to the level of detail or granularity in an image or a spatial dataset. It is a measure of the smallest discernible or resolvable features in the spatial domain, typically...

A technique for obtaining improved resolution of images produced by large telescopes and distorted by the effects of atmospheric turbulence. Many individual exposures are recorded at high speeds by a...

Spectral repeatability refers to the consistency and reproducibility of spectral measurements across multiple trials or instances. It is a measure of how well a measurement instrument or system can...

Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.

An analytical technique used to determine, identify and localize impending malfunctions. It is based upon quantitative and qualitative measurement of submicroscopic particles suspended in lubricating...

Spectroscopy is a technique used in the study of interactions between matter and electromagnetic radiation. It involves measuring and analyzing how different materials absorb, emit, or scatter light,...

Radiation emitted when a quantum mechanical system drops spontaneously from an excited level to a lower level. This radiation is emitted according to the laws of probability without regard to the...

A telescopic light-sensing meter used to measure illumination levels of small regions at a distance of many feet; it is used in professional motion picture and television production to ensure proper...

The splitting or shifting of spectral lines or energy levels caused by the application of a strong transverse electrical field. It often is studied with a canal-ray tube that has a third electrode...

STED microscopy, or stimulated emission depletion microscopy, is a superresolution imaging technique in fluorescence microscopy that surpasses the diffraction limit, enabling the visualization of...

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...

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...

A synchrotron is a type of particle accelerator that uses magnetic fields to steer charged particles, typically electrons or positrons, in a closed, circular or elliptical path. The name synchrotron...