Optical Anisotropy

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optical anisotropy

[′äp·tə·kəl ‚an·ə′sä·trə·pē]
The behavior of a medium, or of a single molecule, whose effect on electromagnetic radiation depends on the direction of propagation of the radiation.

Optical Anisotropy


the difference in the optical properties of a medium as a function of the direction of propagation of optical radiation (light) in the medium and of the state of polarization of the radiation. Optical anisotropy, especially in crystal optics, is frequently understood to mean only the phenomenon of double refraction. However, it is more correct to also classify rotation of the plane of polarization, which occurs in optically active substances, as optical anisotropy.

The natural optical anisotropy of most crystals is due to the character of their structure (the difference in different directions of the field of forces binding the particles in the crystal lattice) and, in the case of some optically active crystals, also to the peculiarities of the excited state of the electrons and “ion cores” in the crystals. The natural optical activity (rotation of the plane of polarization) of substances that manifest it in any state of aggregation (crystalline, amorphous, liquid, or gaseous) is related to the asymmetric structure of the individual molecules of the substances and to the differences—resulting from this asymmetry—in the interactions of the molecules with variously polarized radiation.

Induced (artificial) optical activity arises in media that are by nature optically isotropic, upon exposure to external fields that single out certain directions in the media. These may be an electric field (the Kerr effect), a magnetic field (the Cotton-Mouton and Faraday effects), or a field of elastic forces (the phenomenon of photoelasticity). Double refraction in a fluid flow (the Maxwell effect) and in media through which light fluxes of superhigh intensity (usually laser radiation) are transmitted is also classified as artificial optical anisotropy.


References in periodicals archive ?
Note that, if we chose the mean refractive index of the medium constant with respect to the tensile stretch [[[eta].sub.av]([lambda]) = [[lambda].sub.av](0)], as it was previously taken in the modeling of rubber optical anisotropy [7, 8], the experimental data deviates slightly from the simulated intermediate model curve, but it will be still between the upper and lower limits of the refractive indices band (see Fig.
As pointed out by Wu and Van Der Giessen [5, 8], the three-chain model tends to overestimate the optical anisotropy and the mechanical response at large stretch, relative to the Intermediate network model, while the eight-chain model tends to underestimate it.
For flexible polymer solutions and melts, the net optical anisotropy due to flow can be obtained by measuring the differences in refractive indices in the direction of the principal stresses.
The mechanical anisotropy increases with increasing rolled ratio which is in good agreement with the optical anisotropy results.
Together, Eqs 2, 3, and 4 completely describe the optical anisotropy of the medium for generalized stretch states.

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