Hybrid electrostatic–piezo MEMS photonic integrated modulators

Programmable photonic integrated circuits (PICs) have recently emerged as an important technology for quantum information science and artificial neural networks. In particular, PICs with microelectromechanical-based modulators have the advantages of voltage-based control, ultra-low-energy consumption, cryogenic compatibility, and CMOS-foundry support. Here, we report a cantilever optical modulator that utilizes hybrid piezoelectric and electrostatic tuning forces together on a monolithic silicon nitride (SiN) PIC platform. The device achieves actuation of visible-wavelength light with quasi-static tuning up to 10 kHz at 1.5 Vπ-cm as well as high-speed (>20 MHz) AC modulation with dynamically adjustable (25–40 MHz) mechanical resonances. We report the physics of how geometric nonlinearities, such as capacitive pull-in, give rise to suspended and contacted cantilever modes. These reversible operating regimes generate different strain profiles and boundary conditions, which are responsible for the active tuning of the mechanical resonances. Our proof-of-concept electrostatic–piezo modulator shows promising potential in large-scale programmable PICs applied to high-speed optical switching and optomechanical sensing.