Abstract: A liquid crystal is used as the phase modulating medium in a microwave phase modulating cell (20). Applied electric and/or magnetic fields transverse to the direction of wave propagation create a birefringence that changes the velocity of wave propagation and the index of refraction of the medium. The phase modulating cell (20) is used singly or in arrays to direct microwave beams.

Abstract: A composite material (20) has electrically conducting, elongated particles (22) dispersed in a liquid crystal (24). The index of refraction to microwaves is controllable by the application of a transverse electric field that aligns the liquid crystal material (24) and the particles (22). A phase modulating cell (31) is formed by placing the composite material (20) inside a microwave wave guide (32), with transverse electrodes (36) built into the sides of the wave guide (32). Another set of transverse electrodes or magnet pole pieces (30) can be provided to align the liquid crystal material (24) and the particles (22) in another direction, thereby switching the index of refraction of the cell (31). The particles (22) may be made of a ferromagnetic material, to permit magentic as well as electrical switching.

Abstract: A polymer dispersed liquid crystal (PDLC) film, along with various fabrication methods that enable partial prealignment of the film's LC bubbles, are described. The film is formed with a matrix of liquid crystal bubbles. Individual liquid crystals within the bubbles are partially, but substantially less than fully, aligned in a given direction. Partial alignment is attained by the controlled application of an electric or magnetic field, or a mechanical flow, during photopolymerization. The resulting films retain the positive qualities of prior PDLCs, and in addition exhibit generally lower threshold and operating voltages, and can be used as tunable birefringent films in the infrared region.