Focusing polychromatic light through scattering media

We demonstrate enhanced focusing of polychromatic light through strongly scattering media. The experimental results validate a theoretical relationship among source bandwidth, sample bandwidth, and initial contrast of a far-field speckle. For various combinations of source bandwidth and sample bandwidth, we optimize far-field focal intensity enhancement using a MEMS spatial light modulator to modulate the source beam prior to its propagation through the medium. We achieve focus optimization using a sequential coordinate descent algorithm and Hadamard basis functions to control the spatial phase of the modulator. Enhancement, the ratio of optimized focal intensity to initial speckle mean intensity, is shown to vary monotonically with initial contrast.