Focusing and scanning through scattering media in microseconds

Abstract

Recent advances in computational wavefront shaping have made optical focusing through scattering media a reality. However, most current techniques are too slow to focus, much less image through dynamically changing living biological tissue, such as blood-perfused neural networks, which can decorrelate in milliseconds. We introduce a phase control technique using programmable acoustic optic deflectors (AODs) that is orders of magnitude faster than existing wavefront shaping methods. It is based on sending an array of RF-encoded beams through the medium and measuring the phases of all scattered beams simultaneously with a fast single-pixel detector in just 10 μs. Using the AODs, we then phase conjugate the beams to form a spatio-temporal focus. We also demonstrate two-dimensional scanning of the focus on a sub-millisecond time scale.