Single-Crystal Silicon Photonic-Crystal Fiber-Tip Pressure Sensors

The combination of high-mechanical flexibility and high-optical reflectivity makes planar photonic crystal diaphragms excellent mirrors for optical resonators used in fiber-optic pressure sensing. We have developed a standard silicon process to construct a monolithic photonic crystal-based crystalline silicon membrane. We report on three photonic crystal pressure sensors with different compliances, and discuss the following figures of merit: spectral shift sensitivity; optical sensitivity; pressure sensitivity; resolution; and dynamic range. When compared with a sensor made with an oxide diaphragm, each of our sensors is at least an order of magnitude more sensitive, with a spectral shift sensitivity magnitude of up to 8.6 nm/kPa. We show that the fabrication can be tailored to optimize figures of merit depending on the needs of the application.