Modes laser addressed devices

Figure 2. Schematic drawing of a normal mode laser-addressed SmA device showing the initial clear state (homeotropic alignment) and the laser-addressed and storage (focal conic) states. Methods 1 - 3 are alternative processes for erasure.

Figure 3. Schematic diagram of a rever e mode laser-addressed SmA device showing the initial lightscattering state, the isotropic laser-addressed region, and the clear storage state produced by. simultaneously cooling and applying a small field across the film. Three alternative proce.sses for erasure are shown.

An improvement of this device has been described in which the nematic-cholesteric mixture is replaced by a smectic material. Thermal writing induces the change of the smectic from the perpendicular to a scattering texture. Unlike the nematic-cholesteric materials, selective erasure is possible with the smectic device. The thermal writing is too slow for television-rate applications because of the thermal inertia of the glass-liquid-crystal system. With a laser-beam power of 20 mW, addressing speed is approximately 10 elements/sec for the smectic device. In the projection mode, the resolution is 50 lines/mm at a contrast ratio of approximately 10 1. 

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