# Investigation of the Spatial Generation of Stimulated Raman Scattering Using Computer Simulation and Experimentation

## TL;DR

This paper studies how stimulated Raman scattering is generated in space using simulations and experiments to improve 3D molecular imaging.

## Contribution

The study provides new insights into the spatial generation of stimulated Raman scattering through combined simulation and experimental analysis.

## Key findings

- The spatial width of the stimulated Raman scattering region was 0.21 mm in experiments and 0.09 mm in simulations.
- Most stimulated Raman scattering occurs near the pump beam focus, with Stokes intensity peaking shortly after pump intensity.
- Increasing pump power affects the spatial distribution of Raman gain and signal growth.

## Abstract

Stimulated Raman scattering is a phenomenon with potential use in providing real-time molecular information in three-dimensions (3D) of a sample using imaging. For precise imaging, the knowledge about the spatial generation of stimulated Raman scattering is essential. To investigate the spatial behavior in an idealized case, computer simulations and experiments were performed. For the computer simulations, diffraction theory was used for the beam propagation complemented with nonlinear phase modulation describing the interaction between the light and matter. For the experiments, a volume of ethanol was illuminated by an expanded light beam and a plane inside the volume was imaged in transmission. For generating stimulated Raman scattering, a pump beam was focused into this volume and led to a beam dump after passing the volume. The pulse duration of the two beams were 6 ns and the pump beam energy ranged from 1 to 27 mJ. The effect of increasing pump power on the spatial distribution of the Raman gain and the spatial growth of the signal at different interaction lengths between the beam and the sample was investigated. The spatial width of the region where the stimulated Raman scattering signal was generated for experiments and simulation was 0.21 and 0.09 mm, respectively. The experimental and simulation results showed that most of the stimulated Raman scattering is generated close to the pump beam focus and the maximum peak of the Stokes intensity spatially comes shortly after the peak of the pump intensity.

Graphical Abstract