Optomechanics investigates the interactions between mechanical and electromagnetic degrees of freedom. Over the past 3 decades, this approach has imposed as paradigmatic for the experimental study of fundamental processes in motion continuous measurement, and preparing non-classical motional states of macroscopic mechanical bodies. Currently, the main hurdle for pushing deep in the quantum regime essentially stems from decoherence due to an infinite cohort of optical and mechanical modes, which 'leak' noises into the optomechanical mode of interest. The overall context of this experimental internship is to address this fundamental issue. The idea is to deploy a novel approach, based on the measurement of the full matrix capturing the optomechanically-induced interactions between all mechanical and optical modes. Using information theory, we expect to gain full control over the multimode properties of the optomechanical system, and in particular to deeply suppress off-resonant coupling contributions by, that is the main contribution to decoherence, by tuning the illumination using wavefront shaping. The project will be based on early results already obtained in our group and will be conducted in the frame of an ANR collaboration.