4. Applications

The main drawback of a scattering medium in optical problems is that there is no obvious link between the shape of the incident wave and the output optical field. Such a medium has seemingly lost the memory of the incident wave and it is virtually impossible, without a priori data about the medium, to transmit information from one side of it to the other.

Unlike conventional optical techniques, we have data on the medium: the transmission matrix. Transmitting information from one side to the other means either shaping the output wave (experimentally, this is limited to focusing on one or more points at the output of the medium), or imaging through the medium. Finding the input knowing the output, or finding the input to apply to obtain the desired output, are two rigorously similar problems. In the general case of a linear system described by a known but noisy matrix...