A fly-inspired directional microphone with integrated-photonic microring resonator transduction

Photonic integrated circuits offer compactness, wafer-scale manufacturability and a fast-maturing fabrication base. Here we report what is, to our knowledge, the first fly-inspired directional microphone transduced by integrated photonics: two silicon-nitride microring resonators on opposite wings of a rocking diaphragm, monolithically released above a backside Bosch-etched cavity. Off-axis sound drives the antisymmetric rocking mode, straining one ring in tension and the other in compression; with the laser biased on each ring’s resonance slope, the opposite resonance shifts become two intensity signals of opposite phase, whose difference transduces the direction-bearing motion. The packaged device shows loaded optical quality factors of 18,635 and 17,974 near 1553 nm; scanning laser-Doppler vibrometry resolves the rocking mode near 15.8 kHz and the bending mode near 20.8 kHz. Tone-burst excitation at the two modal resonances demonstrates directional transduction directly in the time domain: at 90° incidence the two ring outputs oscillate in antiphase and their difference is enhanced, whereas at 180° they are in phase and the difference is suppressed. The optical response appears only after the acoustic time-of-flight and rings down after the drive ends, excluding electromagnetic pickup. Finite-element projections of an audio-band device, using shot-noise scaling, indicate an A-weighted signal-to-noise ratio of 74.6 dB(A), more than 10 dB beyond an optimized piezoelectric implementation of the same mechanics. These results constitute a proof-of-concept demonstration of a new transduction platform for chip-scale directional acoustic sensing, with a quantitative roadmap — higher optical quality factor, power— toward practical performance improvement.