Photoacoustic transducer

An integrated photoacoustic transducer for assisting in sensing a concentration of a species in a fluid, the species interacting with radiation by absorption in at least one spectral region, comprising:

• a waveguide structure configured as an optical resonator for enhancing a received radiation signal modulated at a modulation frequency, the waveguide structure having at least one associated optical resonance spectrally overlapping with one of said spectral regions of absorption of radiation by said species,
• at least one acoustic cavity formed in a portion of the waveguide structure and configured to receive the fluid for sensing comprising said species at said concentration so that the fluid can be heated by irradiating it with said enhanced radiation signal, thereby generating an acoustic signal, the at least one acoustic cavity having at least one associated acoustic resonance spectrally overlapping with a harmonic of the modulation frequency,
• at least one acoustic transducer comprising a deformable mechanical portion, the deformable mechanical portion being in direct acoustic communication with the at least one acoustic cavity and having an associated mechanical resonance, the mechanical resonance being adjusted, or the at least one acoustic transducer being configured to allow adjusting of the mechanical resonance over a spectral range, to spectrally overlap with an acoustic resonance associated with the at least one acoustic cavity when the photoacoustic transducer is in use for assisting in sensing said concentration of said species.