CAVITY OPTICAL TRANSDUCER PLATFORM WITH INTEGRATED ACTUATION FOR MULTIPLE SENSING APPLICATIONS

We present an on-chip cavity optomechanical transducer platform that combines high measurement bandwidth and very low displacement noise floor with compactness, robustness, small size, and potential for low cost batch fabrication inherent in micro-electro- mechanical- systems (MEMS) [1]. Our fiber-pigtailed transducers use surface-micromachined silicon-on-insulator photonic, low-stress silicon nitride structural and metal electrical actuation layers, while front- and backside bulk micromachining defines v-grooves and overhanging cantilevers. The motion of the mechanical devices, such as cantilevers and high mechanical quality factor membrane resonators, is optically measured by integrated silicon micro disk optical cavities. The devices can be actuated electrothermally or electrostatically, and this actuation can also be used to tune readout gain. A displacement noise floor below 10 fm/√Hz is achieved for mechanical devices with stiffnesses varying over three orders of magnitude (≈ 0.2 N/m to ≈ 200 N/m). The combination of electrical actuation, low-loss mechanics, and optomechanical readout will enable a wide variety of high-performance on-chip resonant and non-resonant sensors.