Direct digital control of an efficient silicon+liquid crystal phase shifter

We demonstrate a phase shifter based on a silicon slot waveguide infiltrated with liquid crystal. We achieve a phase shift of 73 π for a 5V drive voltage, with a voltage-length product of 0.022V·mm around 1V. We can drive the phase shifter directly with a 1V, duobinary pulse-width-modulated signal, allowing direct digital CMOS control of an analog optical phase shifter.