Design and fabrication of optical-MEMS pressure sensor arrays

Arrays of pressure sensors utilizing microelectromechanical systems (MEMS) technology for fabrication of the sensing element and interrogation by fiber optics are described. Optically interrogated MEMS devices are potentially more suitable for many propulsion applications involving harsh environments than electrically interrogated MEMS devices. Pressure sensor elements form a Fabry-Perot interferometer so that reflected light measures pressure. Rationale for the design of the geometry of sensor elements and array configurations will be presented. These devices are designed to provide sensitivity over a given pressure range, ease of fabrication, and array configurations useful for propulsion characterization. Sensor element and array fabrication will be discussed. These sensor elements are fabricated by etching shallow cavities in glass substrates followed by electrostatic bonding of silicon onto the glass over the cavity. The silicon is then etched to form the pressure sensitive diaphragm. Linear arrays having 6 elements will be described. Experimental results for static pressure tests and dynamic pressure tests carried out in a shock tube demonstrate reasonable linearity, sensitivity and time response.