Abstract: Narrow-band optical filters are disclosed utilizing a birefringent crystal exhibiting a change in sign in birefringence at a predetermined wavelength and relying upon wave coupling between ordinary and extraordinary polarizations of light at or near the predetermined wavelength. The crystal is disposed along the light path between appropriately oriented polarizers, and a dc electric field is applied to the crystal either parallel or perpendicular to the light path. The dc electric field produces the aforementioned wave coupling for light at the center wavelength of the filter which normally is equal to the predetermined wavelength. The filter center wavelength may be displaced from the predetermined wavelength by employing a spatially periodic electric field.

Abstract: Electronically tunable optical filters are disclosed wherein a spatially varying dc electric field is applied to successive regions of a birefringent crystalline medium disposed between a pair of suitably oriented polarizers along the path of a light beam to be filtered. The dc electric field, which may be either parallel or perpendicular to the light path, electro-optically produces in the birefringent medium an effective oscillation of the optic axis of the medium about the pass direction of the input polarizer in a plane perpendicular to the light path as a function of distance along the light path with a predetermined spatial variation to achieve a desired filter transmission characteristic. The electric field is generated from programmable control voltages to provide a wide variety of filter passband or stopband characteristics.

Abstract: There is disclosed a synchronous traveling wave electro-optic modulator for ultra-wideband infrared laser communications systems which provides optical waveguiding of the laser beam through an interaction distance which is large relative to the diffraction limit of the laser beam and which affords essentially perfect radio frequency and optical velocity synchronism at a relatively high electrical impedance level by appropriate choice of the design parameters of the device. The device comprises an array of very slender rectangular rods of electro-optic material such as cadmium telluride laid end to end in juxtaposition to form a light pipe for an infrared laser beam. The length to cross-section ratio of the light pipe is many times greater than that which is determined by the diffraction limit and consequently the voltage and power required to achieve a given depth of modulation is substantially reduced.