Photonics Dictionary

The decrease in the refractive index at the center of a fiber's core, caused by certain fabrication techniques. Also called profile dip.

The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.

In an optical waveguide, the refractive index as a function of radius.

A laser diode with an output beam contained in the active layer by means of a built-in refractive index profile formed in that layer or in the adjacent cladding layers or both.

A material, often a liquid or cement, whose refractive index is nearly equal to the fiber's core index, used to reduce Fresnel reflection from a fiber end face.

Generally, a rotatable table with scales marked in degrees. The fiducial marking also may be a vernier scale. The same scheme is applied to linear movement. Such devices are often applied to...

The ratio of the speed of light in a vacuum divided by the speed of light in the medium.

The absorption index represents the imaginary component of the complex index of refraction, and not the real component. The imaginary component may characterize the attenuation per unit length...

One of the constants h, k, f or I, used to demonstrate any set of parallel planes in a crystal of the hexagonal system.

A CIE index describing the changes in color of standard test objects when the illumination is changed from a standard to a test illuminant.

The ratio of the intensities of two specified spectral lines of a source having vastly different excitation energies. This ratio indicates the level of excitation energy in the source.

A measure of film speed sensitivity to light.

Descriptive of an optical fiber having a core refractive index that decreases almost parabolically and radially outward toward the cladding. This type of fiber combines high bandwidth with moderately...

The term gradient-index profile refers to a specific type of refractive index distribution within an optical material. In optics, the refractive index of a material describes how much the speed of...

For a given mode propagating in a medium of refractive index n, the velocity of light in vacuum c, divided by the group velocity of the mode. For a plane wave of wavelength l, it is related to the...

A superthin, highly reflective mirror.

A measure of the relative difference in refractive index between two optical materials. Most commonly used in fiber optics where the refractive index contrast, D, is given as follows: where n1 equals...

A closely spaced series of well-known chemicals having a refractive index lying between 1.33 for water and 1.95 for a solution of phosphorus in carbon disulfide. They are used to identify powdered...

The description of the refractive index along a fiber diameter.

The mean square difference in refractive index for two separate points in space.

The ratio of the velocities of light in two adjacent media, neither of which is air.

The quantity equal to the refractive index of one medium divided by that of a second medium.

A function of the intensity distribution in an image aberrated by a quadratic curvature wavefront distortion.

An optical fiber in which the core is of uniform refractive index.

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.

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 dispersion relation defined in order to value the reciprocal amount of dispersion. It is defined as the refractivity over the difference in index values of the shortest and longest visible...

Device which measures the index of refraction of glass as well as the dispersion over visible range.

A doped or absorbing transparent medium cut or molded into a wedge in order to measure the real and imaginary components of the refractive index. An internally reflected Gaussian beam is interfered...

The angular change of an incident beam due to vibrational induced refractive index changes within a crystal.

A bulk crystalline optic which permits the propagation of light through a volume of index altered material. The variation in refractive index along the material volume is due to a piezoelectric...

The change in refractive index that occurs as acoustic vibrations are transmitted through an optical material.The index changes are periodic in relation to the frequency, spatial orientation, and...

Anisotropy refers to the property of exhibiting different values or characteristics when measured in different directions. In various fields, including physics, materials science, and geology,...

Dispersion that occurs when the medium's index of refraction decreases as the frequency of the propagating light increases. For a given medium, some wavelength ranges may produce anomalous dispersion...

Irregular propagation of a wave due to variations in the medium's density or refractive index.

A waveguide that has a core with a lower refractive index than the refractive index of the cladding. This structure can limit the power of the transmitted beam by removing unwanted radiation, for...

The unchanging nature of spectral reflectance as vegetational density increases to the point where additional increases in leaf area index or biomass do not cause a change in the spectral reflectance.

Localized variations in the purity and the index of refraction of the atmosphere.

Attenuated total reflectance (ATR) spectroscopy is a technique used in analytical chemistry to obtain IR spectra of samples. It is particularly useful for analyzing solid and liquid samples without...

In fiber optics, the use of a detector to study the range of refractive indices achieved at various wavelengths. This information is calculated electronically to establish the divergence between...

In gradient index optics, a gradient profile in which the refractive index varies along the direction of light propagation, or optical axis. Axial gradient lenses can be used to correct spherical...

A vapor-phase oxidation process for fabricating graded-index optical fibers. It differs from outside vapor phase deposition in that the preform is developed radially rather than longitudinally. An...