Ultrasensitive Diamond Cantilever‐Based Optical Microphone

Microphones are critical for demanding scientific and industrial applications such as photoacoustic spectrometry, medical imaging, nondestructive testing, and trace gas detection. Achieving high sensitivity, low noise, and minimal detection levels in a compact device is a well-known challenge. Herein, a novel diamond cantilever-based optical microphone (DCOM) is reported using a Fabry-Perot interferometric configuration. The DCOM achieves ultrahigh sensitivity (51.5 VPa^-1) and a record detection level (0.018 µPa/ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msqrt><mml:mi>Hz</mml:mi></mml:msqrt> <mml:annotation>$\rm {\sqrt {Hz}}$</mml:annotation></mml:semantics> </mml:math> ), placing it among the highest-performing optical microphones reported to date. The outstanding performance of the DCOM can be attributed to the high quality factor and low intrinsic thermal noise of the diamond cantilever. Furthermore, the DCOM is applied in far-field acoustic sensing and its long-term stability is tested in corrosive environments. These results highlight the DCOM's potential for demanding industrial applications.