Optical Fiber-Tip Monolithic Silicon Pressure Sensors

Fiber-tip interferometric pressure sensors offer high resolution over broad frequency and dynamic ranges with minimal device footprint. We fabricate a 100 μm wide monolithic silicon pressure-sensing-diaphragm and reference cavity as a unit on the wafer-scale, simplifying the packaging. The 1.0 μm thick diaphragm and 1 μm thick cavity form a pressure-sensitive optical resonator which we interrogate over an optical fiber with a polished turning mirror. Our sensors function at pressures up to 3.5 atm, and have tunable dynamic ranges and sensitivities through choice of operational wavelength. We demonstrate 0.002 atm resolution over a 0.9 atm dynamic range using 1544 nm light for atmospheric pressure testing. We introduce an optical model for fiber-tip Fabry-Pérot sensors with diffraction-loss and show good agreement with experimental results. We test the devices in a wind-tunnel environment and demonstrate broad-bandwidth operation and resolution competitive with standard microelectromechanical sensors.