Selective modulation of Infrared radiation by an [Al.sub.2][O.sub.3] particles--liquid crystal system

We have developed a dual-frequency liquid crystal consisting of 4-n-pentyl-4'-cyanobiphenyl (5CB), 4-hexyloxyphenyl-4'- hexyloxy-3-nitrobenzoate (C2), and 4-butyl-4'-(hexyloxyphenyloxycarbonyl)phenyl carbonate (H22). We have measured the frequency dependences of the longitudinal and transverse components of the dielectric constant of the mixture and we have determined the frequency regions of positive and negative dielectric anisotropy. We show that for certain changes in the frequency of the applied electric field while the magnitude of the field remains the same, the transmission region of the [Al.sub.2][O.sub.3] particles--dual-frequency liquid crystal system switches from one wavelength to the other. The experimental results are explained by the optical homogeneity of the system in a narrow wavelength interval when the refractive indices of the particle material and the matrix are close, and also by reorientation of the liquid crystal molecules as the frequency of the applied voltage changes.