Photonics Dictionary

The equation devised by Sir G.B. Airy for the analysis of light diffraction near a caustic surface: (d2f/dz2) - zf = 0 where z represents the independent variable, and f is the value of the function.

In image processing, methods of reducing image defects that result from false data. Techniques include sampling, linear intensity, filtering a high-resolution image to produce a low-resolution image,...

The monochromatic transparency effect produced by the immersion of a finely powdered substance (e.g., glass or quartz) into a liquid with a similar refractive index.

A transparent powdered solid immersed in a liquid or plastic of similar refractive index but widely different dispersion; used to isolate narrow spectral regions.

A lidar (light detection and ranging) technique used in pollution monitoring. Two light beams are emitted simultaneously, one at a wavelength that will be absorbed by the target particles, and the...

Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast microscopy, is an optical imaging technique used in microscopy to enhance the contrast of transparent...

A device that produces an interferogram that can be directly related to the temperature gradient and thereby provides a direct measure of the convective heat transfer coefficients.

The variation in attenuation among the propagating modes of an optical fiber.

A variation in propagation delay caused by differences in group velocity among modes of an optical fiber. Also called multimode group delay, this effect is commonly due to imperfections or any...

A type of phase-shift keying using a one-bit delay line.

A method of coding image data by storing in memory only differences in brightness of each pixel from that of its nearest horizontal neighbors: that is, it is the change in brightness rather than the...

The slope of the curve when output is plotted against input for quantum efficiency in a device.

The measurement of the spectrum bands formed by a spectroscopic sample, based on the differences between the sample and the reference cell it is placed in.

The amount of energy required to raise the energy level of an atom; a necessity if the atom is to radiate energy. High excitation potential is the amount of energy in the upper state of the...

Inertial confinement fusion (ICF) is a method of achieving nuclear fusion, a process where two atomic nuclei combine to release energy. In the case of inertial confinement fusion, the fusion reaction...

Inertial fusion energy (IFE) refers to a proposed method of generating electricity by harnessing the energy released from the fusion of light atomic nuclei, typically isotopes of hydrogen, through a...

An absorbing coating medium between fibers, used in some fused fiber optic plates to absorb unwanted light. Such coatings are sometimes called EMA (extramural absorption).

A position inside a crystal lattice that is not one of the proper lattice sites in the crystal. Impurity ions of the proper size can occupy such positions in an otherwise regular lattice.

The amount of energy required for a particular kind of atom to remove an electron to infinite distance. The ionization potential is usually expressed in volts.

Obeying Lambert's cosine law.

An optical source that has a luminous distribution that is uniform for all directions.

In optics, a plane that emits a flux proportional to the cosine of the angle of the normal; dense opal glass is an example.

A perfectly diffusing surface; the intensity of the light emanating in a given direction from any small surface component is proportional to the cosine of the angle of the normal to the surface. The...

A device to modulate spatially a collimated coherent beam of light with input data in optical data processing. It uses a photocathode mounted on a microchannel plate, which amplifies an electron...

A photon-counting instrument for use in both space-borne and ground-based photometric and spectroscopic instrumentation. This style of detector is composed of opaque photocathodes for photon to...

Totally coherent radiation is produced by a purely monochromatic point source. In the real world the energy will have a limited bandwidth and the point source will subtend some angle resulting in...

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

Raster scanning process like that of television: each line is scanned successively.

The maintenance of a fixed-phase relationship across the full diameter of a cross section of a laser beam.

The spatial distribution of incident and collected flux contained in the analysis of reflectance, transmittance or densities.

1. Generally, an emulsion mask having a clean annular region in an otherwise opaque region. It is designed to eliminate undesired information. 2. A pinhole in a metal plate, placed at a focal plane...

In image processing, the enhancement of an image by increasing or decreasing its spatial frequencies.

With a repetitive object such as a series of equispaced lines, the reciprocal of the line spacing in object or image, generally expressed in cycles per millimeter.

A beam instability, induced by index of refraction inhomogeneities and component damage of dirt and dust particles, that exhibits exponential growth and causes both system degradation and energy loss...

Spatial light interference microscopy (SLIM) is an optical microscopy technique that belongs to the category of quantitative phase imaging methods. It is designed to provide high-resolution,...

A spatial light modulator (SLM) is an optical device that modulates or manipulates the amplitude, phase, or polarization of light in two dimensions, typically in the form of an array. SLMs are...

Also known as transverse mode. The configurations of energy storage, relative to the structure of a laser resonator, that define the relative intensity distribution of the laser beam.

The change in position of the image of a sine wave object from its ideal position. Usually measured in degrees with 360° designating a full cycle of the image.

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...

The correlation of radiation between the phases of monochromatic radiation emanating from two separate points.

Spatially offset Raman spectroscopy (SORS) is a technique that extends traditional Raman spectroscopy by incorporating measurements at different spatial offsets. This method allows for the selective...

Optical aberration such that image magnification varies with ray distance from the optical axis in a radial distortion.

A simple electrostatic lens with a focus controlled by a single potential difference.

Short-distance scattering of light in holography caused by random index inhomogeneities and the developing index that interferes with the incident beam, thus recording a hologram of the scattered...

A method of storing digital data using techniques that consume less memory space than basic methods do. See differential pulse code modulation; run end coding; run length coding.