Photonics Dictionary

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...

A spectral signature, in the context of remote sensing and spectroscopy, refers to the unique pattern or characteristic spectral response of a material or object across different wavelengths of the...

A spectrophotometer is a scientific instrument used to measure the intensity of light at various wavelengths in the electromagnetic spectrum, typically in the visible and ultraviolet regions. It is...

An instrument for plotting the rotatory dispersion of a substance at different wavelengths.

A spectroradiometer is a device used to measure the intensity of light at different wavelengths across the electromagnetic spectrum. It provides a detailed spectral distribution of light, breaking...

The light flash, produced in flash photolysis, that is triggered within a second discharge tube by the third electrode. It is to be differentiated from the photolysis flash which is triggered within...

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,...

Spherical aberration is an optical aberration that occurs when light rays passing through a lens or curved optical surface do not converge or diverge to a single focal point. Instead of focusing to a...

A sputtering target is a solid material used in the process of physical vapor deposition (PVD), specifically sputtering. Sputtering targets are typically made of metals, metal alloys, or compounds...

A type of laser used when a great amount of power is required. Avoiding the bulk of large numbers of optical lenses, this instrument offers high-output intensity and a small emitting region at...

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

A profile of an optical component, usually a fiber, in which the core is of uniform refractive index and the cladding or surrounding optical surface of a different, usually lower, index.

The ability to perceive binocularly the apparent depth and relative distance of objects.

1. A stereoscope that has adjustable scales to allow the determination of distances and dimensions from stereoscopic photographs. 2. A device used to view pictures of the same section of the night...

A rangefinder similar to a pair of binoculars with a long base, a dot or other wander mark provided in each eyepiece field, together forming an apparent point in space. When one dot is moved...

Vision in depth of three dimensions as a result of the spacing of the eyes. This spacing allows the eyes to see objects from slightly different points of view.

In Stimulated Brillouin Scattering (SBS), an incident photon (usually laser light) interacts with acoustic phonons in a medium. The energy and momentum of the incident photon are transferred to the...

Radiation similar in origin to spontaneous emission but determined by the presence of other radiation having the same frequency. Because the phase and amplitude of the stimulated wave depend on the...

Stochastic optical reconstruction microscopy (STORM) is a superresolution microscopy technique that enables imaging of biological specimens at resolutions beyond the diffraction limit of conventional...

Interval between cutting off a photoconductor's signal and the fall of current output to 90 percent.

In polarization-preserving optical fibers, the element used to induce birefringence. The SAP is highly doped to provide a different coefficient of expansion from the rest of the fiber material; when...

An imperfection in optical glass consisting of a distinct streak of transparent material having a slightly different refractive index from the body of glass. It is caused by improper mixing of...

Wavy transparent line in a sheet of glass appearing as though a thread of glass had been incorporated into the sheet.

The pattern formed by a character generation cathode-ray tube system, in which the characters are composed of a sequence of line segments (strokes) generated by the electron beam motion with time...

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.