Time-of-flight resolved stimulated Raman scattering microscopy using counter-propagating ultraslow Bessel light bullets generation

Abstract

We present a novel time-of-flight resolved Bessel light bullet-enabled stimulated Raman scattering (B²-SRS) microscopy for deeper tissue 3D chemical imaging with high resolution without a need for mechanical z-scanning. To accomplish the tasks, we conceive a unique method to enable optical sectioning by generating the counter-propagating pump and Stokes Bessel light bullets in the sample, in which the group velocities of the Bessel light bullets are made ultraslow (e.g., v_g ≈ 0.1c) and tunable by introducing programmable angular dispersions with a spatial light modulator. We theoretically analyze the working principle of the collinear multicolor Bessel light bullet generations and velocity controls with the relative time-of-flight resolved detection for SRS 3D deep tissue imaging. We have also built the B²-SRS imaging system and present the first demonstration of B²-SRS microscopy with Bessel light bullets for 3D chemical imaging in a variety of samples (e.g., polymer bead phantoms, biological samples such as spring onion tissue and porcine brain) with high resolution. The B²-SRS technique provides a > 2-fold improvement in imaging depth in porcine brain tissue compared to conventional SRS microscopy. The method of optical sectioning in tissue using counter-propagating ultraslow Bessel light bullets developed in B²-SRS is generic and easy to perform and can be readily extended to other nonlinear optical imaging modalities to advance 3D microscopic imaging in biological and biomedical systems and beyond.

We report a novel time-of-flight resolved stimulated Raman scattering microscopy through counter-propagating ultraslow Bessel light bullets generation to realize deeper tissue 3D chemical imaging with high resolution.