Delivering Broadband Light Deep into Diffusive Media

Abstract

Waves propagate diffusively through disordered media, such as biological tissue, clouds, and paint, due to random scattering. Recent advances in optical wavefront shaping techniques have enabled controlling coherent light propagation in multiple-scattering samples. We overcome wave diffusion to deliver optical energy into a target region of arbitrary size and shape anywhere inside a strong-scattering system. This is particularly important for applications such as photoacoustic microscopy and optogenetics, where light needs to be deposited deep into biological tissue. For monochromatic light, we previously introduced the deposition matrix (DM) $\mathrm{Z}(\omega)$, which maps its input wavefront to the field distribution in the target region [1]. The eigenchannel with the largest eigenvalue provides the wavefront for maximal energy delivery. Since the enhancement is achieved via constructive interference of scattered waves, the optimal wavefront will vary with input wavelength.