Ultralow-VπL Silicon Electro-Optic Directional Coupler Switch with a Liquid Crystal Cladding

An ultralow-VπL photonic switch device is demonstrated utilizing the high optical and electrical field confinement in silicon slot waveguides coupled with the strong electro-optic response of nematic liquid crystals. A silicon photonic directional coupler switch with a modulation efficiency of 0.0195 Vmm and a loss-efficiency product of 0.0624 VdB is achieved. The 1.5 mm long device is based on two-mode interference within a single slot waveguide resulting in a Vπ of 0.013 V and an extinction ratio of ~ 9dB at 1550 nm wavelength. The power consumption of the photonic switch is estimated to be below 0.6 nW and it possesses a response time of <1.5 ms. A comparative performance study between the directional coupler switch and a Mach-Zehnder Interferometer (MZI) switch is performed. The directional coupler switch is projected to have a smaller footprint and lower optical loss compared to a similar design MZI switch making it a strong candidate for switch matrix designs and applications.