PZT based actuator for an efficient electro-optomechanical interaction in Si-photonic integrated circuits

Lead Zirconate Titanate (PZT) is widely used for energy harvesting owing to its strong piezoelectric and electromechanical coupling coefficient as well as high temperature compatibility (Curie point similar to 370 degrees C).(1-3) The heterogeneous integration of a PZT thin film on the Si photonics platform can compensate the lack of piezoelectricity in the centro-symmetric Silicon, and enable a wide range of electro-optomechanical applications combining the benefits of a strong piezoelectric material and a matured photonic platform. In this work, we directly deposit a PZT film on silicon-on-insulator (SOI) using a transparent Lanthanide based seed layer making it photonics compatible,(4) unlike the traditional PZT film grown with a metallic Platinum (Pt) buffer layer, which introduces unacceptable optical losses in the device.(5) We fabricate unimorph micro-cantilever beams with the hybrid PZT-SOI chip and demonstrate its piezoelectric actuation. The laser Doppler Vibrometry (LDV) measurements on these suspended actuators give a deflection up to 40 nm with an applied RF voltage of V-pp = 10 V at the fundamental resonance frequency. Next, through numerical simulations, we show that a PZT actuator integrated with a directional coupler allows for a strong tuning efficiency. Thus, we demonstrate a PZT film based actuator that can be directly integrated on the Si photonic platform. This opens the possibility of achieving an efficient electro-optomechanical coupling and low-power MEMS applications in Si photonic integrated circuits (PICs).