Scattering invariant modes of light in complex media

Random scattering of light in disordered media is an intriguing phenomenon of fundamental relevance to various applications. While techniques such as wavefront shaping and transmission matrix measurements have enabled remarkable progress for advanced imaging concepts, the most successful strategy to obtain clear images through a disordered medium remains the filtering of ballistic light. Ballistic photons with a scattering-free propagation are, however, exponentially rare and no method so far can increase their proportion. To address these limitations, we introduce and experimentally implement here a new set of optical states that we term Scattering Invariant Modes (SIMs), whose transmitted field pattern is the same, irrespective of whether they scatter through a disordered sample or propagate ballistically through a homogeneous medium. We observe SIMs that are only weakly attenuated in dense scattering media, and show in simulations that their correlations with the ballistic light can be used to improve imaging inside scattering materials.