Birefringent anisotropic materials

The number of compensator methods are numerous and will not be discussed in detail here. The interested reader is referred to Refs. 6-8. Basically what is involved is that a known retardation is used to nullify or compensate the retardation induced by the sample. This amounts to putting some birefringent (anisotropic) material into the light path, e.g. a wedge or plate of quartz or calcite. By changing the thickness of such a material the degree of optical retardation can be controlled— recall eqn. (3). 

Refractive index is dimensionless. For anisotropic materials the state of polarization of the light (and its direction, where appropriate) must be defined relative to a reference axis in the sample. It is then customary to quote two refractive indices additionally, the maximum difference between the two indices measured in two mutually perpendicular directions is termed the birefringence of the material. 

Every transparent material has three refractive indices ny, and nz along the three main axes. A material withwx = ny = nz is called isotropic. At least two of these refractive indices differ in anisotropic materials. The difference between each pair of these refractive indices is called the birefringence A . 

BIREFRINGENCE - division of incident light by optically anisotropic materials into (Double two component which are diffracted in different directions. 

At least two of these refractive indices differ in anisotropic materials. The difference between each pair of these refractive indices is called the birefringence An. 

Birefringent material A crystalline anisotropic material having different refractive indices along different axes of the material. A birefringent material has at least two refractive indices. 

When linearly polarized light is incident on an anisotropic material that exhibits birefringence, the light propagates as two plane waves with orthogonal electric field vectors as shown in Figure 7.1.2. The electric field components Ex and Ey of these plane waves can be expressed as shown in Eq. 4 ... 

Birefringence, or double refraction, is the decomposition of a beam of light into two rays, the ordinary ray and the extraordinary ray, when it passes through anisotropic materials. Birefringence is measured as the difference between the greatest and the lowest index of refraction of an anisotropic and transparent material ... 

The property utilized for this method is the birefringence An of optical anisotropic materials. In these materials, which include almost all liquid crystals, the... 

Interference colors. The observations described up to now in this list are obtained with the source light polarized, but the analyzer left out of the optical path. Inserting the analyzer provides additional information and confirmation. If the fiber is isotropic, the field will appear black. Anisotropic materials will show interference colors, the pattern of which is used to determine thickness and birefringence. When a fiber is mormt-ed and rotated, it shows maximum contrast at certain rotation angles and it disappears into the black field of view at other rotation angles. 

Birefringence The difference in the refractive indexes of an anisotropic material can be calculated by subtraction or with a Michel-Levy chart. 

Birefringence - The light is transmitted with equal velocities in an isotropic substance. In anisotropic materials, molecular structure is such that the transmission vibration varies as a funetion of direction. A material is optically anisotropic when its refractive index depends on direetion. Birefringence is calculated as the dififerenee inreirae-tive index in two selected perpendieular direetions. 

Here n (n denotes the fast and slow indices (for anisotropic materials with rod-shaped molecules n = n and = nj, d is the thickness of the birefringent film, and A is the wavelength of the light. The component that feels larger refractive index will be slower, i.e., retarded with respect to the other polarization directions. 

Birefringence A property of optically anisotropic materials in which two or more different orientationally dependent refractive indices are present. 

The average chain orientation in transparent or translucent anisotropic materials can be determined through the measurement of their birefringence. Among the three refractive indices, which correspond to the three directions of space, at least two are different in an anisotropic material. The difference between two of these refractive indexes is the birefringence. 

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