An optomechanical system for transducing an optical intensity modulation movement including an optical detector and a mechanical sensor including a mobile mass, of which a receiving surface is intended to receive an external mechanical urging, and an excitation device. The excitation device is configured to vibrate the mobile mass along an excitation direction at at least one of its resonance frequencies. The vibration of the mobile mass is disrupted by the external mechanical urging, and modifies an evanescent field of the optical detector. The mobile mass has an interaction region facing the optical detector, as well as a second region, respectively having, projecting along a plane perpendicular to the excitation direction, an interaction surface area S.sub.111 and a second surface area S.sub.112, with S.sub.112<S.sub.111.