Cavity-enhanced ultrafast two-dimensional spectroscopy using higher-order modes

TL;DR

This paper introduces a cavity-enhanced ultrafast 2D spectroscopy method using frequency combs and higher-order optical cavity modes, significantly boosting sensitivity for dilute molecular samples.

Contribution

It presents a novel approach combining frequency combs with higher-order cavity modes for background-free, high-sensitivity 2D spectroscopy.

Findings

Signal to noise ratio improves with cavity finesse squared.

Method enables ultrafast 2D spectroscopy in dilute molecular beams.

Background-free phase cycling enhances measurement accuracy.

Abstract

We describe methods using frequency combs and optical resonators for recording two-dimensional (2D) ultrafast spectroscopy signals with high sensitivity. By coupling multiple frequency combs to higher-order modes of one or more optical cavities, background-free, cavity-enhanced 2D spectroscopy signals are naturally generated via phase cycling. As in cavity-enhanced ultrafast transient absorption spectroscopy (CE-TAS), the signal to noise is enhanced by a factor proportional to the cavity finesse squared, so even using cavities of modest finesse, a very high sensitivity is expected, enabling ultrafast 2D spectroscopy experiments in dilute molecular beams.