Scattering liquid crystal in optical attenuator applications

Several possibilities based on the principles of the scattering and polarization of light in liquid crystals and PLZT ceramics were studied for the replacement of mechanical shutters and attenuators in optical instruments. A scatter mode liquid crystal was selected as the active material, and two modules were developed for fiber optic attenuator applications. In the first, the light transmitted through an optical fiber (input fiber, (phi) 100/140 micrometers ) is collimated to a beam using a Selfoc microlens (0.25 P, (phi) 1.8 mm). This beam penetrates two LC cells (7 X 12 mm2) and is received by a Selfoc microlens at the output fiber. The second, for large-diameter fibers ((phi) 400 micrometers ), employed conventional aspherical lenses to optimize the fiber-to-fiber coupling instead of microlenses. Components were built for both (phi) 100 micrometers and (phi) 400 micrometers fibers. The maximum transmission is up to 70% and maximum contrasts 10,000:1 (632.8 nm), 3000:1 (830 nm) and 1200:1 (905 nm). The rise time is typically under 1 ms and the decay time under 5 ms, given a temperature above +20 degree(s)C. The contrast remains high from 0 degree(s)C to +50 degree(s)C. Both components function with +/- 100 VAC.