Monolithic silicon-on-nothing photonic crystal pressure sensor

We present a single-mask process that combines isotropic and anisotropic etching with selective removal of passivation layers followed by hydrogen annealing to yield monolithic crystalline silicon (c-Si) devices. The process is demonstrated by creating pressure sensors that combine photonic crystal (PC) mirror pressure-sensing diaphragms with silicon-on-nothing (SON) reference cavities. The first generation sensors were tested with fiber-optic readout and showed high sensitivity. The single-mask process has sufficient flexibility for application-specific optimization of the PC, diaphragm, and cavity. The monolithic silicon structure gives the sensor potential for good stability. The simple process, robust structure, and integration of all critical components simplifies packaging, which could lead to low-cost mass production.