Utilizing Microcavities to Suppress Third-order Cascades in Fifth-order Raman Spectra

TL;DR

This paper demonstrates that using optical microcavities and quantum electrodynamical modeling can significantly suppress cascading signals in fifth-order Raman spectroscopy, revealing the true nonlinear signals.

Contribution

The study introduces a method to suppress third-order cascades in fifth-order Raman spectra using microcavities and QED, enhancing signal clarity in multidimensional spectroscopy.

Findings

Up to 99.5% suppression of cascading signals achieved.

Optimized cavity size and pulse directions are key to suppression.

QED treatment accurately models cascade suppression mechanisms.

Abstract

Nonlinear optical signals in the condensed phase are often accompanied by sequences of lower-order processes, known as cascades, which share the same phase matching and power dependence on the incoming fields and are thus hard to distinguish. The suppression of cascading in order to reveal the desired nonlinear signal has been a major challenge in multidimensional Raman spectroscopy, i.e., the $\chi^{(5)}$ signal being masked by cascading signals given by a product of two $\chi^{(3)}$ processes. Since cascading originates from the exchange of a virtual photon between molecules, it can be manipulated by performing the experiment in an optical microcavity. Using a quantum electrodynamical (QED) treatment we demonstrate that the $\chi^{(3)}$ cascading contributions can be greatly suppressed. By optimizing the cavity size and the incoming pulse directions, we show that up to $\sim$99.5\% suppression of the cascading signal is possible.