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

摘要

A binary mixture of ferroelectric liquid crystals (FLCs) was used for thedesign of a channel waveguide. The FLCs possess two important functionalities:a chromophore with a high hyperpolarizability $\beta$ and photoreactive groups.The smectic liquid crystal is aligned in layers parallel to the glass plates ina sandwich geometry. This alignment offers several advantages, such as thatmoderate electric fields are sufficient to achieve a high degree of polarorder. The arrangement was then permanently fixed by photopolymerization whichyielded a polar network possessing a high thermal and mechanical stabilitywhich did not show any sign of degradation within the monitored period ofseveral months. The linear and nonlinear optical properties have been measuredand all four independent components of the nonlinear susceptibility tensor$\bar d$ have been determined. The off-resonant $d$-coefficients are remarkablyhigh and comparable to those of the best known inorganic materials. Thealignment led to an inherent channel waveguide for p-polarized light withoutadditional preparation steps. The photopolymerization did not induce scatteringsites in the waveguide and the normalized losses were less than 2 dB/cm. Thematerial offers a great potential for the design of nonlinear optical devicessuch as frequency doublers of low power laser diodes.