Design and Fabrication of Novel Optomechanical Sensors

Abstract

In this thesis, several optomechanical sensors for operation at low and high frequencies areintroduced. These sensors are primarily intended as accelerometer systems for use as precision measurement tools, with applications in a wide range of fields, including gravitational physics, geodesy, seismology, and inertial sensing. They are a highly sensitive, new technology for acceleration measurements which are compact, light weight, and relatively low cost. In particular, such systems are vital in future mass change missions and have many other sensing applications. We present four optical readout methods along with a mechanical modulation scheme for homodyne readouts to mitigate 1/f noise induced by a photodetector readout. These methods include a shadow sensor readout, a fiber Fabry-Perot interferomter readout, a heterodyne interferometer readout, and a Si3N4 waveguide optical ring resonator readout. These optical methods are paired with different resonator systems, depending on size and application. Low and high frequency resonators made from monolithic fused silica or silicon provide systems with large mechanical quality factors (Qs), allowing for compact highly sensitive sensors that function over a broad range of operation temperatures that are vacuum compatible. The resonators presented operate in a linear fundamental mode according to the equation of motion of a damped-spring-mass oscillator. The resonator designs, Si resonator fabrication, mount design, system testing, and current results are presented.