IC compatible optomechanical pressure sensors using Mach-Zehnder interferometry

Sensing using silicon integrated optics enjoys the benefits of both optics and integrated circuit (IC) technologies. The advent of MEMS technologies can potentially lead to a new generation of miniaturized optical sensing devices and systems. In this paper, we present the design, fabrication, and measurement results of silicon integrated optical pressure sensors based on a micromechanical Mach-Zehnder interferometer (MZI). The MZI employs the antiresonant reflecting optical waveguide (ARROW), the fabrication of which is based on standard IC dielectric materials that are also micromachining-compatible, yielding losses as low as 1 dB/cm. The theory and operation of the waveguide as well as sensor transduction principles are described along with a rigorous semi-analytical treatment of the coupled opto-mechanical effects on photonic transport taking into account the anisotropic nature of the MZI mechanical and optical properties. Based on the above analysis, design considerations with corresponding measurement results for two sensor configurations are presented: a single MZI operated in push-pull mode which yields a sensitivity enhancement of 80% yielding 180 μrads/Pa relative to the nonpush-pull counterpart, and a dual-MZI configuration for removal of ambiguity associated with multiple fringes