Slow-light enhanced silicon photonic crystal phase tuner actuated by electrostatic comb drives

This paper presents the design, fabrication, and experimental demonstration of a silicon photonic phase tuner that leverages slow-light effects in a suspended photonic crystal (PC) slot waveguide. The phase is tuned by electrostatic comb actuation which modulates the slot width within the PC defect thus achieving a high phase sensitivity enhancement relative to a conventional slot waveguide. The device is fabricated using a silicon photonic foundry process followed by post-processing steps to remove the oxide cladding and suspend the PC slot waveguide and electrostatic actuation combs. The design exhibits up to a 16-fold improvement in phase sensitivity, enabling sub-volt <i>V</i> _π with a nominal slot width of 200 nm. A small actuation length of just 33 <i>μ</i>m results in a <i>V</i> _π <i>L</i> of 20.13 V<i>μ</i>m. The results demonstrate phase tuning with complementary metal-oxide-semiconductor (CMOS) compatible core voltages for high density, high speed applications in silicon photonics, such as optical phased arrays and photonic accelerators.