Highly sensitive silicon micro-g accelerometers with optical output

This paper reports a bulk, micro machined, out-of-plane, optical accelerometer with high sensitivity and micro-g resolution. A custom fabrication process, based on SOI wafers, has been adopted to reduce the residual stress acting on the free-standing devices as well as to increase the flatness of the released surfaces. The conceived optical sensing strategy allows operation in the visible range, based on novel photonic band gap (PBG) materials, named "transparent metals". The integration with, photo-detectors, and electronic in silicon can be easily realized. In order to obtain optimal results, several different prototypes have been designed and realized. The generic device is composed by a central silicon proof mass sustained by four symmetric beams anchored to its four corners. A mechanical noise floor of 0.1 μg/sqr(Hz) has been estimated whereas a value corresponding to 0.3% of the incoming radiation per mg is deduced for the sensitivity.