2ND-HARMONIC GENERATION IN ANTIFERROELECTRIC LIQUID-CRYSTAL

We present the first observation of second-harmonic generation (SHG) i n the phase-matched condition in an antiferroelectric liquid crystal ( AFLC). The SH intensity profile suggests the C2 symmetry instead of th e D2 symmetry expected in the ideal helicoid-unwound AFLC structure. T his discrepancy is interpreted by the structural change from D2 to C2 symmetry due to a pretransitional effect of the electric-field-induced antiferroelectric-ferroelectric phase transition.