Silicon on sapphire CMOS architectures for interferometric array readout

The performance of microelectromechanical sensor systems relies critically on the transduction method employed to convert the mechanical displacement into an electrical signal. Optical readout techniques have distinct advantages over more traditional capacitive and piezoelectricity transduction methods. They are employed in applications where atomic resolution with small sensing area is necessary, for example scanning probe microscopes. In this paper, we present two architectures for optoelectronic sensing based on silicon on sapphire CMOS (SOS-CMOS) technology. We show how to heterogeneously integrate photodetectors, analog CMOS signal processing circuits, and VCSEL's for an array based optical readout system. The optical transparency of the sapphire substrate allows for the design of both a Michelson and Fabry-Perot type interferometers that are amenable to 2D array sensing. We present preliminary experimental data demonstrating standing wave detection in the lOOnm thin silicon PIN photodiodes available in the SOS-CMOS technology for the Fabry-Perot interferometer .