Abstract
We demonstrate an acoustic sensor based on a Fabry–Perot interferometer formed by a single-mode fibre and an external silicon photonic-crystal mirror. Measurements in air indicate that this sensor has a relatively uniform frequency response up to at least 50 kHz, and detects pressures as low as 18 μPa Hz−1/2. This limit is four orders of magnitude lower than in similar types of acoustic fibre sensors. The sensor response agrees with mechanical calculations to within a few dB. We predict that this sensor has the potential to detect pressures as low as 600 nPa Hz−1/2, corresponding to the ambient thermal noise level in air at room temperature.
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