TYPE-II PHASE-MATCHED 2ND-HARMONIC GENERATION IN FERROELECTRIC LIQUID-CRYSTALS

The experimental configurations that permit phase-matched second-harmo nic generation in ferroelectric liquid crystals have been analyzed. Th e materials have been assumed to behave as uniaxial positive with norm al wavelength dispersion of refractive indices. It has been found that both type I and type II phase matching an possible for a general conf iguration and the corresponding effective second-order susceptibility coefficients have been calculated. However, with the usual homeotropic geometry, only type I phase matching can be achieved. Under planar al ignment, types I and II are accessible in theory, but the large birefr ingence of most materials usually prevents both possibilities. Neverth eless, a compound, whose properties are suitable for type II phase mat ching observation, has been found. The effect has been confirmed exper imentally and the results agree well with the theory.