Gradient-assisted focusing light through scattering media

Focusing light through a scattering medium is a long-standing challenge in biomedical optics, to which wavefront shaping is a powerful solution. The state-of-the-art feedback-based approach is the widely used genetic algorithm method. However, it can only achieve relatively low enhancement of the focus, and the genetic algorithm is known to be time-consuming. To tackle those issues, we propose a gradient-assisted strategy for wavefront shaping. The proposed method conducts optimization in the function distribution space. Specifically, when optimizing the parameters along each iteration, the consequent function distribution changes within a distance as measured by the Kullback-Leibler divergence. Taking advantage of the gradient information, the proposed method is over 60x faster to obtain the same peak-to-background ratio (PBR) level. Compared with the genetic algorithm that is able to optimize a number of 64 x 64 phase segments, the proposed gradient strategy is able to optimize 256 x 256 phase segments, and gives 20x higher focus enhancement as quantified by the PBR. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Automated summary

This study presents a gradient-assisted wavefront shaping strategy that is faster and achieves higher focus enhancement compared to genetic algorithms. By optimizing parameters in the function distribution space and utilizing gradient information, the proposed method outperforms genetic algorithms in terms of speed and focus enhancement, as quantified by the peak-to-background ratio (PBR).