Speaker
Description
If we put a several tens of microns thin sample of nematic liquid crystal with planar alignment
of molecules with respect to the LC cell surface in between two crossed plane polarizers,
illuminate it by white light and rotate appropriately, then using a fiber optic spectrometer we
can observe a quasi-periodic spectral distribution of intensity of light behind the output
polarizer. The spectral distribution of intensity of light emerges due to liquid crystal
birefringence. Based on the polarizability models from which imply models describing the
extraordinary and ordinary refractive indices n e a n o , respectively, the phase birefringence
dispersion function of LC in the spectral region of wavelengths without resonant frequencies
can be expressed. Comparison of the measured spectrum with that obtained by calculation
according to the model one can find parameters characterizing mean resonance (absorption)
wavelengths as well as coefficients expressing the strength of the influence of these
absorption bands to resulting birefringence. The approach could complement absorption or
ellipsometric measurements the aim of which was to characterize optical properties of a liquid
crystal sample.
