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Abstract
Using a pulsed, pump-probe experimental arrangement, we have investigated the speckle generated by a 100 μm path length cell of smectic A liquid crystal 4-cyano-4′-octylbiphenyl doped with 0·1 wt% dichroic dye. Upon irradiation, the guest-host system undergoes a phase transition from an initially transparent condition to a scattering state. We show that the statistical theory of speckle can be used to describe the evolution of scattering domains and estimate an rms refractive index variation of 0·0021 within the irradiated region for one case. Dynamic response as a function of molecular anchoring conditions was also investigated.