Phase Retrieval Approach for Transmission Matrix Identification in Polytetrafluoroethylene (PTFE)

We present a phase retrieval approach for identifying the transmission matrix (TM) of highly scattering media, specifically PTFE. Utilising structured illumination via a Digital Micromirror Device (DMD) and Wirtinger Flow optimization, our method reconstructs complex TM elements from intensity-only measurements without the need for reference beams. This enables robust, real-time wavefront shaping applicable to biomedical imaging. Experimental results demonstrate high fidelity in TM recovery and spatial focusing efficiency, validating the feasibility of this approach in practical scenarios. A comparative evaluation of two measurement strategies –random phase masks versus one-to-one actuator mapping – is presented, demonstrating the practical implications of each method.