Numerical study of reflection-based energy density enhancement in turbid media via wavefront shaping

Delivering energy deep into turbid media is essential for applications like biomedical imaging, medical treatment, and material processing. We applied wavefront shaping to enhance light penetration by manipulating the phase of incident light. Using feedback-based phase optimization and numerical solutions of Maxwell's equations, we present an approach that significantly and non-invasively increases the energy density deep inside complex scattering media by minimizing the reflected light, without prior knowledge of the media. In simulations of media with a transport mean free path as low as $43.36\mu \text{m}$ , we achieved a 2.5-fold enhancement of the energy density at a depth of about $200\mu \text{m}$ . Light transport through this simulated medium is equivalent to propagation through approximately $4\text{mm}$ of biological tissue with optical properties typically found in the red or infrared wavelength range. By switching between minimized and maximized reflection, the energy density can be modulated by up to a factor of 12 deep inside the scattering medium, while the energy density at shallow depths remains fairly unchanged.