Nonlinear transmission spectroscopy with dual frequency combs

TL;DR

This paper demonstrates how dual frequency combs can be used for nonlinear transmission spectroscopy to detect various electronic and vibrational resonances in molecules, with control over spectral features via phase shaping.

Contribution

It introduces a method using two frequency combs to measure single-photon, two-photon absorption, and Raman resonances through radio frequency modulation detection.

Findings

Selective detection of TPA and Raman resonances independent of carrier frequency

Single-photon resonances identified by specific transmission signals

Spectral phase shaping influences TPA but not Raman resonances

Abstract

We show how two frequency combs $\mathcal{E}_1$, $\mathcal{E}_2$ can be used to measure single-photon, two-photon absorption (TPA), and Raman resonances in a molecule with three electronic bands, by detecting the radio frequency modulation of the nonlinear transmission signal. Some peaks are independent of the carrier frequency of the comb and others shift with that frequency and have a width close to the comb width. TPA and Raman resonances independent of the carrier frequency are selected by measuring the transmission signal $\sim\mathcal{E}_1^2 \mathcal{E}_2^2$ and the single-photon resonances are selected by measuring the transmission signal $\sim\mathcal{E}_1^3\mathcal{E}_2$. Sinusoidal spectral phase shaping strongly affects the TPA, but not the Raman resonances.