An acoustic ring
resonator employing a two-dimensional surface
phononic crystal is proposed for high-sensitivity detection in binary
gas mixtures. Band analyses and frequency-domain simulations via the
finite-element method reveal that a single band for spoof surface
acoustic waves appears at ultrasonic frequencies around 58 kHz where
modification of its dispersion due to varying gas composition results
in a linear shift of the resonance frequency. The shift rate is −17.3
and 8.8 mHz/ppm for CO2 and CH4, respectively.
The linear shift of resonance frequency is experimentally validated.
In addition, the ring resonator can also be employed to track acoustic
intensity variation with gas concentration, where exponentially decaying
intensity for low concentrations leverages high-sensitivity operation.
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