Abstract
Polysilicon microbeams in integral vacuum enclosures on silicon substrates have optical and mechanical properties that provide excellent opportunities for fiber-optic sensors. The microbeam, shell, and silicon substrate form a structure with Fabry-Perot-like properties that functions as an optomechanical modulator. When the beam vibrates incident light is modulated and reflected light is used to sense vibration of the beam. Thus, the structure can be used as a mechanical vibration or acoustic emission sensor. Microbeams attached to the substrate at both ends are highly strain sensitive and form the basis of a variety of sensors, including pressure sensors, accelerometers, strain, vibration, and temperature sensors. Excitation at the wafer level by a polymer film piezoelectric transducer provides a simple non-contact optical method for testing the microbeams before the water is cut into sensor die. Modulated light from a laser diode can also be use to excite the microbeams into resonance. The test results suggest that optically resonant microbeams can be used for low-cost precision fiber-optic sensors. Fiber-optic sensors are especially attractive for aerospace applications because optical fibers provide wide-bandwidth communication capability while eliminating electromagnetic interference (EMI), ground loops, and shielding requirements.
