Design and Fabrication of Monolithic Photonic Crystal Fiber Acoustic Sensor

Single-crystal silicon is an excellent optical and mechanical material, but its properties are compromised by the incorporation of other materials required for functionality or structural support. Here, we describe a monolithic silicon acoustic sensor based on a sensing diaphragm with an integrated photonic crystal (PC) mirror. Diaphragm deflection is measured in a Fabry-Perot resonator formed between the PC mirror and a gold coated single-mode fiber. The sensors are fabricated on standard silicon wafers by standard CMOS processing technologies, yielding monolithic, low-stress sensing diaphragms. The packaged sensor exhibits a minimum detectable pressure of 10 μPa/√(Hz) in the 8-17-kHz frequency range.