Electrically Tunable Liquid-Crystal-Core Optical Channel Waveguide

We report electrically tunable liquid-crystal-core channel waveguides, in which the lightwave guiding can be tuned among cut-off, single-mode, and multi-mode. Ultrasonic-assisted chemical etching is used to produce semicircular grooves on the optical glass substrate for encapsulating liquid crystal as the waveguide core. The liquid-crystal-core waveguide loss is reduced to the lowest value 1.3 dB/cm up to date, which is attributed to the smooth and uniform groove surface. The extinction ratio is >20 dB for optical switching application. The LC director distributions under various voltages are calculated by finite element method and the characteristics of guided modes are simulated by the full-vectorial mode solver considering the full anisotropy. The simulated waveguide characteristics are well consistent with the experimental results. The proposed liquid-crystal-core waveguide owns the features: simple and low-cost fabrication process, arbitrary device pattern, and integration with silicon platform.