Realization of a liquid crystal electrically controlled optical waveguide on micromachined silicon

In this paper we report the major fabrication steps and preliminary electro-optical characterization of a novel integrated liquid crystal optical waveguide on silicon substrate. The optical waveguide is made of a SiO2/Si V-groove with a triangular cross-section filled with nematic liquid crystal E7. The optical propagation in the channel waveguide is controlled by an external voltage which induces a refractive index variation by means of molecular director reorientation. For TM polarized light at a wavelength of 1.55 μm, a threshold voltage of only about 2 V and an extinction ratio higher than 35 dB were measured with 6.5 V applied.