Combined ellipsometry and refractometry technique for characterisation of liquid crystal based nanocomposites.

Spectroscopic ellipsometry is a technique especially well suited to measure the effective optical properties of a composite material. However, as the sample is optically thick and anisotropic, this technique loses its accuracy for two reasons: anisotropy means that two parameters have to be determined (ordinary and extraordinary indices) and optically thick means a large order of interference. In that case, several dielectric functions can emerge out of the fitting procedure with a similar mean square error and no criterion to discriminate the right solution.

Performances of a polymer-cholesteric-liquidcrystal output-coupler in Nd-doped fiber lasers.

The performances and characteristics of a polymer-cholestericliquid-crystal reflector, used as an output coupler in a Nd-doped fiber laser, are presented. We show that a judicious combination of a linear polarizer and a quarter wave plate with the cholesteric coupler allows for a continuous scanning of the output-intensity from zero to a maximum value following the well-known Malus law. The results are shown to be contained in a simple Jones Matrix formalism.