Optical Microphone Structures Fabricated for Broad Bandwidth and Low Noise

Abstract

A micromachined optical microphone structure using a grating based interferometer has been presented previously and is undergoing continued development (JASA, vol. 118, pp 3000-3009, November 2005). Two advantages of the approach that have been highlighted in prior work are high displacement resolving capability of the microphone diaphragm vibration (2 pm rms over the audio bandwidth) and a flexible mechanical design space for achieving broad bandwidth and low thermal noise designs.Here, we summarize a variety of structures we are fabricating using Sandia National Laboratories silicon-based microfabrication technology to explore this versatile design space. These structures are being packaged to resemble instrumentationtype microphones with approximately 1cm 2 form factor in order to facilitate rigorous acoustic evaluation in the Micromachined Sensors and Transducers Laboratory (MiST) and anechoic test facilities at Georgia Tech.

A Grating Interferometric Acoustic Sensor Based on a Flexible Polymer Diaphragm

“…However, due to the complexity of its demodulation algorithm, the LSMI is not suitable for detecting high-frequency acoustic signals and is limited to detecting infrasound [ 16 ]. Compared to other optical interferometric acoustic sensors, GI-based acoustic sensors could be designed with high integration, wide bandwidth, and high acoustic fidelity [ 17 , 18 ].…”

MEMS sensor array platform integrated with CMOS based optical readout

“…Integration of optical MEMS devices with customized CMOS has been demonstrated for optical microphones [1] and accelerometers [2]. These are either single devices or a small array of a few devices.…”