Nonlinear switching of near infrared light in liquid crystal on silicon channel waveguides

This paper reports on linear and nonlinear optical properties of channel waveguides made of micromachined SiO2/Si V-grooves filled with nematic liquid crystal E7. Experiments demonstrate operation of the waveguides in the C-band (1530 - 1565 nm). Molecular reorientation of the NLC, induced either by an applied low frequency electric field or by the electric field of the light itself, changes the LC refractive index distribution then allowing the control of guided light. Design criteria and techniques of channel waveguides for both electro-optical and all-optical switching and modulation will be discussed. Experiments are presented where it is showed that light at 1550 nm, fiber-coupled to the LC waveguide is optically modulated by an optical beam with an input power below 25 mW. All-optical switching of a signal at 1510 nm with a contrast over 10 dB is also demonstrated by using a copropagating control signal at 1560 nm. A model of the waveguide is also presented able to explain linear and nonlinear experimental results.