Photoacoustic detecting device

A photoacoustic detecting device for measuring a parameter of interest in a medium to analyse, the photoacoustic detecting device comprising:

• a housing comprising a cover and a baseplate, wherein the baseplate comprises an aperture, said housing being configured to house:
• at least one lighting module configured to emit at least one light beam,
• a photoacoustic cell, comprising a contact surface accessible from the aperture of the baseplate, said contact surface being intended to be placed in contact with the medium to analyse, the photoacoustic cell further comprising a photoacoustic cavity extending from the contact surface to a top of the photoacoustic cell, wherein said top and said surface contact are open,
• at least one window closing the top of the photoacoustic cell or the contact surface of the photoacoustic cell,
• at least one subwavelength pattern located on a surface of said window, said subwavelength pattern being configured to focus the light beam on a surface of interest of the medium to analyse,
• a sensor, linked to the photoacoustic cavity, the sensor being configured to detect a generated signal, said generated signal being generated in the photoacoustic cavity by a photothermic effect in the medium to analyse in response to the irradiation of said medium by the light beam, and
• wherein the photoacoustic cell, the window and the subwavelength pattern are formed on a single silicon wafer.