Influence of Magnetic Field on Level of Linearly Polarized Laser Beam Passing through Faraday Crystal

Many natural materials have the ability to rotate the polarization level of linearly polarized laser beam and pass through it. This phenomenon is called optical activity. In the event that a light beam (linearly polarized) passes through an optically active material, such as a quartz crystal, and projected vertically on the optical axis, the output beam will be polarized equatorially, and the vibration level will rotate at a certain angle [1], [2], [3]. A number of crystals, liquids, solutions, and vapors rotate the electric field of linearly polarized light that passes through them [4], [5], [6], [7]. Many different physical effects are applied to optical isotropic and transparent materials that cause them to behave as optical active materials, where they are able to rotate the polarization level of the polarized light linearly and pass through it [8], [9], [10]. These effects include mechanical strength, electric field, and magnetic field. By placing one of these effects on an optically transparent medium, it changes the behavior of the light travelling through it [11].

Amorphous Silicon as an Active Material in Optical Resonators

The application of amorphous silicon as a thermo-optically active material in MEMS-based, tunable optical filters is presented. The thin film interference filter employs a solid-state silicon cavity and silicon-based distributed Bragg reflectors (DBR). Tuning is achieved by varying the the resonator's refractive index and thus its optical thickness through thermal modulation. The filter is configured as a membrane and operates up to a temperature of 450 °C. Such a filter is essential for monitoring and reconfiguration of optical data communication networks and is also applicable for chemical and gas sensing.

ELECTRO-OPTIC AND ELECTRO-GYRATION EFFECTS IN CHIRAL MOLECULAR SYSTEMS

The linear electro-optic (EO) and electro-gyration (EG) effects are studied in an optically active material systems including Bi 12 SiO 20 (BSO) oxide and bent-core liquid crystals. In an isotropic BSO sample, the breaking of intrinsic centro-symmetry allowed the EO modulation of the refractive index. In a mixture of bent-shaped liquid crystalline molecules having both optical activity and birefringence, the observed intensity modulation is investigated, which is related to the nonlinear optical responses of both the optical rotatory power and the birefringence. Both the linear EO and EG effects are understood in terms of the superposition principle of linear and circular birefringences.

Critical Pitch in Thin Cholesteric Films with Homeotropic Boundaries

Calculations of the planar cholesteric texture with homeotropic boundary conditions are presented. At a constant film thickness there is a critical twist t0c below which the planar texture has transformed into a homeotropic one. The additional influence of an external field is discussed for positive and negative anisotropy and with field orientations parallel or normal to the film plane. A general solution of the director field has been found for a normal orientation of the field. A properly adjusted twist t0 obtained by dilution of an optically active material in a nematic matrix opens a possibility to reduce the critical voltage in technical devices.