Shaped two-photon excitation deep inside scattering tissue

TL;DR

This paper investigates how wavefront shaping combined with temporal focusing can enable deep, three-dimensional two-photon excitation inside scattering tissue, demonstrating robustness up to 550 micrometers depth.

Contribution

It provides a comprehensive theoretical and experimental analysis of scattering effects on wavefront shaped beams for deep tissue excitation, highlighting the robustness of temporally focused patterns.

Findings

Temporal focusing enhances robustness against scattering.

Deep excitation up to 550 μm achieved.

Wavefront shaping enables 3D confinement in scattering tissue.

Abstract

Light is the tool of the 21st century. New photosensitive tools offer the possibility to monitor and control neuronal activity from the sub-cellular to the integrative level. This ongoing revolution has motivated the development of new optical methods for light stimulation. Among them, it has been recently demonstrated that a promising approach is based on the use of wavefront shaping to generate optically confined extended excitation patterns. This was achieved by combining the technique of temporal focusing with different approaches for lateral light shaping including low numerical aperture Gaussian beams, holographic beams and beams created with the generalized phase contrast mthod. What is needed now is a precise characterization of the effect of scattering on hese different methods in order to extend their use for in depth excitation. Here we present a theoretical and experimental study on the effect of scattering on the propagation of wavefront shaped beams. Results from fixed and acute cortical slices show that temporally focused spatial patterns are extremely robust against the effects of scattering and this permits their three-dimensional confinement for depths up to 550 {\mu}m.