Photonics Dictionary

Fluorescence correlation spectroscopy (FCS) is a powerful analytical technique used to study the dynamics and interactions of fluorescently labeled molecules in solution at the single-molecule level....

A fluorescent screen refers to a phosphorescent or fluorescent-coated surface that emits visible light when exposed to other forms of electromagnetic radiation, such as x-rays or ultraviolet light....

A device used to scan, with a small, intensely bright spot, portions of a picture surface and to transform the original picture into a series of electrical signals. In optical character recognition,...

A plane (through the focal point) at right angles to the principal axis of a lens or mirror; that surface on which the best image is formed.

A retroreflector that can focus a beam of light, with one planar reflective surface, one spherical and a third that is either planar or convex cylindrical.

1. A term used to describe the clouded appearance of an incompletely polished surface that scatters light. 2. The accumulation of moisture on an optical surface. 3. The extra spectral blackening of a...

1. A flaw in a blank caused by folding the blank's surface during its formation. 2. The change in the direction of a system's optical axis caused by a reflective component.

1. The sector of the Earth's surface registered upon a remote sensing device in a satellite. 2. The amount of space occupied by a component on the surface upon which it is mounted. 3. The space on an...

A laser skin-resurfacing method that creates microscopic thermal wounds referred to as microscopic treatment zones (MTZs), which are surrounded by uninjured tissue. The MTZs are usually arranged in a...

The process whereby a rotating wheel carries grains of an abrasive, suspended in a vehicle, across the surface of the optical glass to be ground. The workpieces are forced downward by pneumatic...

A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a beam of accelerated electrons as the lasing medium. Unlike traditional...

The frequency space between consecutive transmission peaks in the transmission spectrum of a Fabry-Perot interferometer or etalon. The free-spectral range is inversely proportional to the distance...

Freeform mirrors refer to reflective optical components that deviate from traditional symmetric or rotationally symmetric shapes, such as spheres or paraboloids. Unlike conventional mirrors, which...

Freeform optics refers to the design and fabrication of optical surfaces that do not follow traditional symmetric shapes, such as spheres or aspheres. Unlike standard optical components with...

The multiple beam form of Brewster's fringes formed when the two plane-parallel plates have high-reflecting surfaces.

The distance between the front focal point and the vertex of the front surface.

Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin concentration in the brain. It utilizes near-infrared light to penetrate the...

Optical fibers fused together to form a solid, vacuum-tight assembly in the form of a slab or rod. Discs or rectangular shapes having ground and polished surfaces perpendicular to the fiber lengths...

An instrument used to detect and measure the energy distribution of gamma rays. It has been used to chart the radioactivity at the lunar surface.

The global ecosystem dynamics investigation (GEDI) lidar is a state-of-the-art spaceborne instrument designed to study Earth's forests and ecosystems in three dimensions. Developed by NASA, GEDI is...

A rapid roughing process for the quick removal of glass, the first step in manufacture of a curved lens surface. It is accomplished with coarse emery or a diamond-impregnated tool.

Trade name referring to an instrument that determines surface distances by measuring the length of time it takes for a modulated lightwave to reach a mirror and be reflected to its point of origin.

The area of optics in which the propagation of light is described by geometrical lines (or rays) governed by Fermat's Principle. Geometrical optics is useful as long as the objects in which the light...

Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing or inactivating microorganisms, including bacteria, viruses, and fungi. The...

A noncrystalline, inorganic mixture of various metallic oxides fused by heating with glassifiers such as silica, or boric or phosphoric oxides. Common window or bottle glass is a mixture of soda,...

The specular reflection of individual parts of a surface.

The total radiation, both solar and diffuse sky, that is incident to a unit's horizontal surface.

A crystal of microscopic size having no definite plane faces and having a globular shape. At the time the crystal is formed, the strong surface tension influences the formation of the plane faces.

Property of a surface which, because of directional reflection, is responsible for the degree to which reflected highlights or the images of objects may be seen as superimposed on the surface.

Gold colloid aggregates refer to clusters or assemblies of gold nanoparticles suspended in a liquid medium. These aggregates are formed when individual gold nanoparticles come together due to various...

A mirror whose percent reflectance varies as a function of position on the mirror surface.

A grating beamsplitter is an optical device that utilizes the principles of diffraction to split a beam of light into multiple beams, often redirecting them at specific angles. It is based on the...

The substrate upon which a diffraction grating will be ruled. It must be dimensionally stable, and the surface must be polished to an accurate flat or spherical form as required by the grating. The...

An instrument capable of precise measurements of the Earth's gravity. This permits the detection of small changes in local height that indicate changes in the Earth's crust and subsurface density.

1. A measure of absorbed dose, equal to the energy imparted by ionizing radiation to a mass of matter corresponding to 1 J per kilogram. 2. A term used to denote an incompletely polished surface that...

A condition in which an emergent ray is perpendicular to the normal of the emergent surface of a medium.

Light striking a surface at an angle almost perpendicular to the normal.

A porous ceramic substance that is ground to a given optical form and on which a polished plate of glass is sagged by heat application. It is capable of transmitting in a partial vacuum. The glass...

A GRIN (gradient index) lens is a type of optical lens that utilizes a gradient in refractive index across its volume rather than having a uniform refractive index like conventional lenses. This...

A tool of cast iron or another suitable medium used with a slurry of silicon carbide, aluminum oxide or emery for grinding optical surfaces.

A defect in the cleaved end face of an optical fiber, defined as multiple surface irregularities across the fiber surface. A less serious imperfection of the same nature is known as mist.

1. In a cathode-ray tube, the glow surrounding a bright spot that appears on the fluorescent screen as the result of the screen's light being reflected by the front and rear surfaces of the tube's...

Describing a surface that is coated with a film of metal of such thickness that it transmits about one-half of the incident light and reflects about one-half.

In the most general sense, the resistance of a solid surface to damage.

An aggravated form of fog in a polished surface caused by the scattering of light. The defects causing haze are larger than those causing fog, but singly are not large enough to be seen by the...

A head-up display (HUD) is a transparent display technology that presents information directly in the field of view of a user, typically without requiring the user to look away from their usual...

A calorimetric calculation from which the temperature vs. time dependence of any point on a sample can be determined, provided surface and bulk absorption, thermal conductivity and heat transfer...

A heat sink for a laser is a device designed to absorb and dissipate the excess heat generated by the laser during operation. This is crucial to maintain the laser's performance, prevent overheating,...