Rapid broadband characterization of scattering medium using hyperspectral imaging

Antoine Boniface,Sylvain Gigan,Kishan Dholakia,Ivan Gusachenko

doi:10.1364/optica.6.000274

Abstract

Scattering of a coherent ultrashort pulse of light by a disordered medium results in a complex spatiotemporal speckle pattern. The form of the pattern can be described by knowledge of a spectrally dependent transmission matrix, which can in turn be used to shape the propagation of the pulse through the medium. We introduce a method for rapid measurement of this matrix for the entire spectrum of the pulse based on a hyperspectral imaging system that is close to 2 orders of magnitude faster than any approach previously reported. We demonstrate narrowband as well as spatiotemporal refocusing of a femtosecond pulse temporally stretched to several picoseconds after propagation through a multiply scattering medium. This enables new routes for multiphoton imaging and manipulation through complex media.

Highlights

Light propagation in a disordered medium gives rise to scattering
RESULTS we report on performances of the technique through a different wavefront shaping experiment, showcasing the ability of the measured MSTM to allow spatial and temporal focusing of a pulse
The required input field is calculated by first choosing the monochromatic transmission matrix (TM) for the desired wavelength and performing complex conjugation on the TM column corresponding to the desired spatial position [9]

Summary

Introduction

When the size of the medium becomes large compared to the scattering mean free path, the transmitted light is multiply scattered This poses a major depth limitation for conventional imaging techniques, in particular imaging through biological tissues, due to exponential attenuation of unscattered light. The measurement of the transmission matrix and the ability to control the incident wavefront by means of dynamic diffractive optics have opened the possibility to control speckle patterns and shape the output in complex media. It has created a wealth of new applications, in particular in scattering tissue imaging and in mesoscopic physics that studies such elusive phenomena as the presence of open and closed channels in scattering media [1]

Methods

Results

Conclusion