Nonlinear optical properties of a channel waveguide produced with crosslinkable ferroelectric liquid crystals

A binary mixture of ferroelectric liquid crystals (FLCs) was used for the d esign of a channel waveguide. The FLCs possess two important functionalitie s: a chromophore with a high hyperpolarizability beta and photoreactive gro ups. The smectic liquid crystal is aligned in layers parallel to the glass plates in a sandwich geometry. This alignment offers several advantages, su ch as that moderate electric fields are sufficient to achieve a high degree of polar order. The arrangement was then permanently fixed by photopolymer ization which yielded a polar network possessing a high thermal and mechani cal stability which did not show any sign of degradation within the monitor ed period of several months. The linear and nonlinear optical properties ha ve been measured and all four independent components of the nonlinear susce ptibility tensor (d) over bar have been determined. The off-resonant d-coef ficients are remarkably high and comparable to those of the best known inor ganic materials. The alignment led to an inherent channel waveguide for p-p olarized light without additional preparation steps. The photopolymerizatio n did not induce scattering sites in the waveguide and the normalized losse s were less than 2 dB/cm. The material offers a great potential for the des ign of nonlinear optical devices such as frequency doublers of low-power la ser diodes.