Second-Harmonic Generation in Achiral Bent-Shaped Liquid Crystals

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Abstract
Second-harmonic generation (SHG) has been observed as functions of temperature, electric field and incidence angle in the liquid crystal phases of the achiral bent-shaped molecules with octyloxy end chains (P-8-O-PIMB). In the highest temperature B2 phase, the SHG for oblique incidence started to appear at an electric field when the texture change due to the electric-field-induced molecular and dipolar reorientations occured. The SHG interferometry clearly indicated the reversal of polarization on reversing the applied field in the B2 phase. The other two phases, B3 and B4, were also SHG active even in the absence of the field, indicating the spontaneous polar ordering in these phases. It was found that similar compounds with hexyloxy end chains (P-6-O-PIMB) and octyl end chains (P-8-PIMB) are not SHG active.