TEMPERATURE-DEPENDENCE OF THE 2ND-ORDER SUSCEPTIBILITY IN CALAMITIC FERROELECTRIC LIQUID-CRYSTALS

The d(ij) coefficients of the second-order susceptibility tensor for s econd harmonic generation were detemined for a calamitic ferroelectric liquid crystal (FLC) specifically designed for applications in non-li near optics. The measurements were performed at different temperatures in the SmC phase. In accordance with the design methodology of these materials, the coefficient along the polar axis d(22) is the greatest , and depicts an expected behaviour in the whole range of the ferroele ctric phase. On the other hand, the temperature dependence of d(21), d (23), and d(25), is anomalous to some extent, including a sign inversi on of d(23) at a certain temperature. These results, which contrast wi th those reported recently for non-calamitic FLCs, were qualitatively interpreted in the light of different conformations which, by virtue o f plausible distortions of the molecular core, could coexist in the sa mple.