Nematic Liquid Crystal Optical Channel Waveguides on Silicon

We demonstrate the first channel waveguides made of E7 nematic liquid crystal (LC) in SiO₂-Si V-grooves. The grooves have been obtained by wet etching n-Si substrates first and then by thermally growing an approximately 2-mum-thick SiO₂ cladding layer. Propagation of infrared light at a wavelength of 1550 nm shows a good optical confinement in 10-mum-wide LC waveguides. Modal analysis and beam propagation simulations predict single mode propagation. This is experimentally confirmed by the acquired near field images. The optical waveguide acts as an integrated optic polarizer, since only vertical polarization can propagate due to the orientation of the LC molecules. The horizontal polarization state is suppressed by more than 25 dB