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 μ Pa / Hz in the 8 kHz to 17 kHz frequency range.