2ND-HARMONIC GENERATION IN ACHIRAL BENT-SHAPED LIQUID-CRYSTALS

Second-harmonic generation (SHG) has been observed as functions of tem perature, electric field and incidence angle in the liquid crystal pha ses of the achiral bent-shaped molecules with octyloxy end chains (P-8 -O-PIMB), In the highest temperature B-2 phase, the SHG for oblique in cidence started to appear at an electric field when the texture change due to the electric-field-induced molecular and dipolar reorientation s occured. The SHG interferometry clearly indicated the reversal of po larization on reversing the applied field in the B-2 phase. The other two phases, B-3 and B-4, were also SHG active even in the absence of t he field, indicating the spontaneous polar ordering in these phases. I t was found that similar compounds with hexyloxy end chains (P-6-O-PIM B) and octyl end chains (P-8-PIMB) are not SHG active.