Experimental structural characterization of reflection matrices of scattering media

Optical methods for in vivo biomedical applications are fundamentally limited by multiple light scattering, particularly under label-free, reflection-based conditions. Although reflection-matrix approaches have enabled deterministic wavefront control and reconstruction in such environments, their intrinsic structural properties in biologically relevant regimes remain insufficiently characterized. Here, we experimentally measure reflection matrices of scattering media using time-gated interferometric microscopy. Their structure is analyzed from complementary perspectives, including angular off-diagonal structure, singular value decomposition, and spatial-domain speckle statistics. The measured reflection matrices exhibit a consistent near-diagonal angular organization with rapid off-diagonal decorrelation and similar singular value envelopes. At the same time, medium-dependent variations appear in the angular intensity redistribution, effective dimensionality, and spatial correlation length. These results establish experimentally grounded structural descriptors of reflection matrices, providing a quantitative physical baseline for numerical modeling and data-driven reconstruction approaches.