A Novel Cantilever-Based Silicon Photonic Accelerometer Using Mach–Zehnder Interferometer Targeting 10-ng/ $\sqrt{\text{Hz}}$ Noise Floor

Silicon photonics has emerged as a popular platform for building sensors that can perform a wide range of measurements with high sensitivity. Here, an optical accelerometer in a silicon photonics platform was designed, and a fabricated device’s performance was characterized using integrated thermal electric modulators and shaker tests. The device operation is based on the balanced Mach-Zehnder interferometer (MZI) that resides in the top layers of a silicon chip. The chip is packaged to form a cantilever beam. As the chip undergoes acceleration, the reference arm of an MZI maintains a stationary phase while the sensing arm bends. Multiple loops of serpentine waveguides were used to increase sensitivity. When light from the reference and sensing arms is combined, the output light has an intensity that is modulated by the imparted acceleration. These intensity variations are detected by a fiber-coupled photodetector. An analytical model is presented combining optical and mechanical subsystems and is used to identify small designs with sub-10- $\text {ng}/\sqrt {\text {Hz}}$ noise floor. The sensor can transmit analog sensor data over long distances via the attached fiber array, making the sensor attractive for deep subsurface seismic measurements running several km underground at elevated temperatures.