Numerically optimized FROG results for the study of red-shifted spectra in multi-frequency Raman generation

TL;DR

This paper uses numerically optimized FROG and a novel interference model to analyze red-shifted spectra in multi-frequency Raman generation driven by chirped pulses, revealing linear Raman processes as the origin.

Contribution

It introduces a double-pulse interference model and employs an adaptive learning-based FROG reconstruction to interpret spectral features in multi-frequency Raman scattering.

Findings

Good agreement between simulations and experiments

Red-shifted component arises from linear Raman processes

Spectral broadening shows asymmetric features

Abstract

When multifrequency Raman scattering is driven in the transient regime by two chirped pump pulses, the resulting anti-Stokes orders exhibit asymmetric spectral broadening toward lower frequencies, leading to a characteristic double-peaked structure in each order. In this Letter, frequency-resolved optical gating (FROG) is used to investigate the spectral evolution of the first anti-Stokes Raman component. To interpret the observed features, we introduce a double-pulse interference model and employ an adaptive learning-based reconstruction algorithm using the Adam optimizer to retrieve the temporal field evolution. The simulation results show good agreement with the experimental measurements. Our analysis indicates that the observed red-shifted spectral component originates from linear Raman processes within the two-photon dressed-state framework.