Photonics Dictionary

Exhibiting the characteristic of materials that are electrical insulators or in which an electric field can be sustained with a minimum dispersion of power. They exhibit nonlinear properties, such as...

A shallow, fine-pitch diffraction grating having a precise dielectric overcoating that experimentally has absorbed wavelength-specific incident light that is polarized in the P-plane.

A high-reflectance coating consisting of alternating layers of quarter-wave film of a higher refractive index and lower refractive index than the substrate. Such coatings can be made very specific to...

A number that indicates the magnitude of the shift in a solid of positive and negative charges in opposite directions when a voltage is applied across the solid.

A crystal that is characterized by its relatively poor electrical conductance.

A waveguide made up of a dielectric material, such as plastic or mica, in a cylindrical form, through which the waves travel.

A lens made up of a dielectric material that is capable of influencing radio waves much in the same way an optical lens influences light.

The minimum of change in stimulation needed to effect an awareness of change in sensation that is statistically determined.

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.

Differential mode delay (DMD) is a parameter used to characterize the propagation characteristics of optical fibers, particularly in multimode fiber optic systems. It refers to the difference in...

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.

As a wavefront of light passes by an opaque edge or through an opening, secondary weaker wavefronts are generated, apparently originating at that edge. These secondary wavefronts will interfere with...

The angle that lies between the direction of an incident light beam and any resulting diffracted beam.

Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs light into specific diffraction orders or achieves a desired optical effect....

The formation of a fan of light or energy rays in a beam as the beam passes through an extremely narrow aperture.

A spectrograph that uses a diffraction grating as its dispersive element in place of a prism, and yields greater resolving power, more dispersion and a linear spectrum.

A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel grooves or rulings. These rulings act as an array of closely spaced slits...

The property of an optical system whereby only the effects of diffraction determine the quality of the image it produces.

The interference pattern formed by light waves diffracted at the edges of an object as seen on a screen placed in their path.

1. The ring patterns of light that seem to encircle particles in the field of a microscope. 2. See Newton's rings.

Elastic scattering that occurs when inelastic processes eliminate particles from the beam.

In spectroscopy, the parallel bands that vary in lightness and darkness or color, and that are formed when light is diffracted by a sample.

A lens with aberrations corrected to the point that residual wavefront errors are substantially less than one-quarter the wavelength of the energy being acted upon.

Any optical device that utilizes diffraction in an image-forming capability. Familiar diffractive lenses are zone plates, holographic lenses, kinoform lenses and binary optics.

Optical elements that use diffraction to control wavefronts. Diffractive optical elements include diffraction gratings, surface-relief diffractive lenses, holographic optical elements and...

A measurement device used to study the structure of matter using the diffraction of electromagnetic radiation.

The study of the diffraction of beams of a wave by matter to ascertain the structure of the matter.

The logarithm of the reciprocal of diffuse transmittance. Diffuse density results when a sample is diffusely illuminated.

Light emitted by one or more sources and characterized by a high degree of scatter.

Modulation transfer function of an optical element when used for transporting images from a lambertian source such as phosphors.

Ratio of diffusely reflected flux to incident flux.

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

Nonspecular reflection from a rough surface.

A reflecting surface that scatters radiation that is incident on it, thus producing diffuse reflection.

Use of a photoelectric receiver to sense an object's presence by detecting a small amount of the emitter's light that is diffusely reflected by the object.

Transmission accompanied by diffusion or scatter to the extent that there is no regular or direct transmission.

The ratio of diffusely transmitted flux to incident flux.

A color filter that is designed to gradually increase or decrease its absorption with wavelength.

An optical diffuser is an optical component or material designed to scatter or diffuse light that passes through it. It is used to create a more even or uniform illumination, reduce glare, or soften...

A filter purposely made to be placed before a lens to render the image rather unclear.