Photonics Dictionary: A

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...

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...