Investigation of a Liquid Crystal Acousto-Optic Conversion Cell
An acousto-optic conversion cell using nematic liquid crystals provides a low-cost method for planar detection of an ultrasonic radiation field. Although the information received is somewhat rudimentary, in some cases it could be considered as a replacement for an array of transducers. Nematic liquid crystals are fluids that, because of the long-range order of the orientation of their long molecules, are optically uniaxial. Proper surface treatment of a substrate will cause the molecules--and the optic axis--to align normal to the surface, and a thin layer of material between two treated glass plates will have uniform alignment throughout the volume with the optic axis normal to the plates. This is the usual configuration of an acousto-optic conversion cell. When placed between crossed polarizers, light at normal incidence is blocked, but mechanical (or electrical) perturbations will cause the optic axis to tip and light to be transmitted. Because of the weakness of the elastic restoring forces for orientational distortions, very weak perturbations are observable.
KeywordsLiquid Crystal Optic Axis Duty Cycle Nematic Liquid Crystal Pulse Height
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