Enhanced phase-matched second-harmonic generation in a ferroelectric liquid crystal waveguide

A binary mixture of crosslinkable ferroelectric liquid crystals (FLCs) was used for the design of a channel waveguide. The liquid crystal was aligned in layers parallel to the glass plates (homeotropic) in a sandwich geometry and then the arrangement was permanently fixed by photopolymerization whic h yielded a polar network possessing a high thermal and mechanical stabilit y. The linear and nonlinear optical properties have been measured and all f our independent components of the nonlinear susceptibility tensor d have be en determined. The off-resonant d-coefficients are remarkably high and comp arable to those of the best known inorganic materials. Phase-matching was a chieved by taking advantage of the modal dispersion of the waveguide. A rev ersal of sign of chi ((2)) at the nodal plane of the electric field distrib ution of the first-order mode was needed to maximize the overlap. integral between the fundamental and the second-harmonic (SH) light. In samples with chi ((2)) inversion the SH Signal was 1000 larger that in samples without chi ((2)) inversion.