MEMS based Fabry Perot pressure sensor and non-adhesive integration on optical fiber by anodic bonding

Optical pressure sensor based on the principle of Fabry Perot interferometry have been developed and fabricated using the technique silicon-to-silicon anodic bonding. This MEMS based Fabry Perot pressure sensor is then integrated onto an optical fiber by a novel technique of anodic bonding. In this novel technique of anodic bonding we use ultra-thin silicon of thickness 10mum to bond the optical fiber to the sensor. Tensile bond strength measurements are performed to characterize the fiber to silicon bond as a function of bonding temperature. The ultra-thin silicon plays the role of a stress reducing layer which helps bonding an optical fiber to silicon having conventional thickness. The pressure sensing membrane is formed by 8mum thick ultra-thin silicon which allows having membrane with uniform thickness over the entire wafer and eliminates the need for bulk etching. The pressure sensor integrated onto an optical fiber is tested for static response and for response with change in ambient temperature. The sensor response changes with the temperature due to change in the physical dimension of the sensor. Also, the effect of multimode fiber on the fringe visibility of the interferometer is studied. The fringe visibility of the sensor is lower than the theoretical fringe visibility due to the fact that one of the mirrors of the Fabry Perot interferometer formed by silicon membrane is not flat but a curved surface.