PHOTOACOUSTIC DETECTING DEVICE

A photoacoustic detecting device (1) for measuring a parameter of interest in a medium to analyse comprises:- a housing (9) comprising a cover (91) and a baseplate (92), wherein the baseplate (92) comprises an aperture, wherein said housing (9) houses:* at least one lighting module (2) configured to emit at least one light beam,* a photoacoustic cell (7), comprising a contact surface (71) accessible from the aperture (921) of the baseplate (92), said contact surface (71) being intended to be placed in contact with the medium to analyse, the photoacoustic cell (7) further comprising a photoacoustic cavity (72) extending from the contact surface (71) to a top (73) of the photoacoustic cell (7), wherein said top (73) and said surface contact (71) are open,* at least one window (74, 75) closing the top (73) of the photoacoustic cell or the contact surface (71) of the photoacoustic cell (7),° at least one subwavelength pattern (8A, 8B, 8C, 8D) located on a surface of said window (74, 75), said subwavelength pattern (8A, 8B, 8C, 8D) being configured to focus the light beam on an surface of interest of the medium to analyse,° a sensor (3), linked to the photoacoustic cavity (72), the sensor (3) being configured to detect a generated signal, said generated signal being generated in the photoacoustic cavity (72) 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 (7), the window (74, 75) and the subwavelength pattern (8A, 8B, 8C, 8D) are formed on a single silicon wafer.