Abstract

We have conducted a detailed experimental study of stimulated scatterings of nanosecond laser pulses from thin films of nematics and smectic, and isotropic cholesteric liquid crystals. We have observed for the first time simultaneous occurrence of phase conjugation (with aberration correction capability) and optical pulse compression (with compressor ratio as high as 20 or so). The origins of the nonlinear scattering process have been studied in detail with linearly and circularly polarized beams and are found to be mostly of Brillouin nature, although Raman and orientational processes also contribute in some cases. We have also studied the process involving some guided wave geometries in thin films of nematic and smectic and observed good quality phase conjugation and pulse compression even under very severe distortion at the input end of the sample. The observed thresholds for the stimulated scattering are in the kilowatts regime, and they are compared and contrasted with observations in other nonlinear materials. In most cases, the laser power thresholds are comparable to other nonlinear liquids, but it is observed that the threshold for a particular cholesteric is unusually low. Detailed analysis and experimental results are presented.

© 1986 Optical Society of America