Transient measurement of phononic states with covariance-based stochastic spectroscopy

TL;DR

This paper introduces a new stochastic covariance-based method for transient Raman spectroscopy that enables detailed measurement of phononic states, revealing information hidden from traditional mean-value techniques.

Contribution

It presents a novel stochastic probe and covariance analysis approach for 2D-Raman spectroscopy, expanding capabilities beyond mean-value-based methods.

Findings

Successful experimental demonstration on alpha-quartz

Recovery of phase, amplitude, and energy of phonon modes

Potential for new nonlinear spectroscopy insights

Abstract

We present a novel approach to transient Raman spectroscopy, which combines stochastic probe pulses and a covariance-based detection to measure stimulated Raman signals in alpha-quartz. A coherent broadband pump is used to simultaneously impulsively excite a range of different phonon modes, and the phase, amplitude, and energy of each mode are independently recovered as a function of the pump-probe delay by a noisy-probe and covariance-based analysis. Our experimental results and the associated theoretical description demonstrate the feasibility of 2D-Raman experiments based on the stochastic probe schemes, with new capabilities not available in equivalent mean-value-based 2D-Raman techniques. This work unlocks the gate for nonlinear spectroscopies to capitalize on the information hidden within the noise and overlooked by a mean-value analysis.