Lasers thin film nematic

Several methods of optical data storage using LCPs are known."" " The preferred thermo-optical system uses a thin (5 to 7 pm) film of a high (60 to 80°C) polymer which has a subsequent liquid crystal phase (either nematic or smectic) up to 20 to 30°C above the Tg. Either bonded to the polymer backbone or simply dispersed in the polymer is a dye, chosen to absorb the laser light used to write on the film. 

If the material is thin (i.e., in nematic liquid crystal fdm), the problem of optical propagation is greatly simplified. In its passage through such a nonlinear film, the laser beam is only phase modulated and suffers negligible amplitude change. In other words, the transmitted far-field intensity pattern is basically a diffraction pattern of the incident field, with the nonlinear film playing the role of an intensity-dependent phase screen. 

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