Micro-optical inertial sensors using silicon MEMS

Polysilicon surface-micromachining offers a new approach to the development of micro-optical systems on silicon. An "optical bench on a chip" with multiple three-dimensional components that are movable has been developed. An accelerometer, which relies measurement of optical intensity change due to the interaction between a light beam and a movable optical filter has been fabricated. The filter consists of a aluminum-coated polysilicon grating that is connected to folded-beam springs that are anchored on the substrate. A 0.5 micron movement of the mass-spring system translated to 150 g acceleration. Simulation of the vibration modes of the mechanical structure indicate that the first natural frequency would occur at 6.9 kHz. A new accelerometer has been designed that can sense 10 g with a 1 micron movement of the filter. Optical interferometric sensors have also been fabricated. These can be also be used in high precision accelerometers. Multi-axis accelerometers can be easily developed in these silicon micro-optical systems.