Covariance spectroscopy of molecular gases using fs pulse bursts created by modulational instability in gas-filled hollow-core fiber

TL;DR

This paper introduces a novel covariance spectroscopy technique using noisy broadband pulse bursts generated by modulational instability in gas-filled hollow-core fibers to probe nonlinear molecular gas processes.

Contribution

It demonstrates a new method for detecting molecular nonlinear processes through spectral correlation analysis of noisy pulse bursts.

Findings

Successful detection of infrared-inactive Raman transitions

Numerical simulations confirm experimental results

Potential improvements in signal strength and spectral resolution

Abstract

We present a technique that uses noisy broadband pulse bursts generated by modulational instability to probe nonlinear processes, including infrared-inactive Raman transitions, in molecular gases. These processes imprint correlations between different regions of the noisy spectrum, which can be detected by acquiring single shot spectra and calculating the Pearson correlation coefficient between the different frequency components. Numerical simulations verify the experimental measurements and are used to further understand the system and discuss methods to improve the signal strength and the spectral resolution of the technique.