Abstract

Second-order nonlinear effects have been observed in chiral smectic C* ferrorelectric liquid crystal (FLC) materials through second harmonic generation (SHG). Recently, we reported new FLC materials with reasonably high nonlinear d coefficients {d₂₂(W3l4) = LiNbO₃}.¹,² With these new nonlinear materials, modulation schemes through the expected large linear electrooptic effect (nanosecond response) should be possible. We present results on novel measurements of the EO coefficient using a prism coupled thin film waveguide technique. Optical TE eigenmodes are excited inside the FLC waveguide, which is sandwiched between two polyvinyl alcohol (PVA) cladding layers supported by a pair of indium-tin-oxide (ITO) coated prisms. By applying a dc biased voltage pulse train, the refractive index of the FLC is modulated by the electric field through the EO effect. This small change of the refractive index then modulates the propagation constant β of the waveguide modes. Preliminary results indicate that the EO coefficient r₃₂ ≈ 0.3 pm/V for the commercially available British Drug House mixture SCE9. Analysis indicates this method is very sensitive compared with alternatives such as the direct interferometric measurement of phase modulation or Fabry-Perot multiple reflection interferometry.

© 1991 Optical Society of America