Focusing and Compression of Ultrashort Pulses through Scattering Media

TL;DR

This paper demonstrates that by controlling only the spatial wavefront, both spatial and temporal distortions of ultrashort pulses in scattering media can be corrected, enabling enhanced nonlinear imaging.

Contribution

It introduces a method to correct spatial and temporal distortions of ultrashort pulses using spatial wavefront shaping alone, improving nonlinear optical imaging through scattering media.

Findings

Refocused pulses can be shorter than input pulses.

Achieved 100-fold enhancement of two-photon fluorescence.

Successfully focused 100fs pulses through brain tissue.

Abstract

Light scattering in inhomogeneous media induces wavefront distortions which pose an inherent limitation in many optical applications. Examples range from microscopy and nanosurgery to astronomy. In recent years, ongoing efforts have made the correction of spatial distortions possible by wavefront shaping techniques. However, when ultrashort pulses are employed scattering induces temporal distortions which hinder their use in nonlinear processes such as in multiphoton microscopy and quantum control experiments. Here we show that correction of both spatial and temporal distortions can be attained by manipulating only the spatial degrees of freedom of the incident wavefront. Moreover, by optimizing a nonlinear signal the refocused pulse can be shorter than the input pulse. We demonstrate focusing of 100fs pulses through a 1mm thick brain tissue, and 1000-fold enhancement of a localized two-photon fluorescence signal. Our results open up new possibilities for optical manipulation and nonlinear imaging in scattering media.