Photoacoustic detecting device comprising a membrane forming a contact face

A photoacoustic detecting device to be applied, via a contact face, against a medium to be analyzed, the device comprising:

• a hollow cavity that is filled with a gas, and that opens onto the contact face;
• a light source that is configured to emit, when it is activated, an incident light beam, in an emission spectral band, through the cavity, to the contact face, the incident light beam being pulsed or amplitude-modulated;
• and
• an acoustic detector connected to the cavity;
• wherein, under an effect of illumination of the medium by the incident light beam, the acoustic detector detects an acoustic wave produced by heating of the medium;
• the device further comprises an interface membrane, forming the contact face, the interface membrane being configured to:
• form an interface between the gas, filling the cavity, and the medium to be analyzed;
• and
• block passage of the medium to be analyzed into the cavity;
• and
• the acoustic detector is configured to detect an acoustic pressure wave, generated inside the cavity, under the effect of a variation in the temperature of the interface membrane, the temperature variation of the interface membrane being induced by the heating of the medium resulting from the illumination of the medium.