Phase‐Stable Multidimensional Coherent Spectroscopy Based on Dual‐Comb Interferometry

Abstract

Multidimensional coherent spectroscopy (MDCS) is a highly intriguing field for the unique capacities to unravel quantum pathways of microscopic dynamics and discern different dipole–dipole interactions. These capabilities are not simultaneously accessible through any other techniques. The foundation of MDCS lies in the stable phase and accurate time information of the multi‐pulse sequences involved. Achieving the phase stability has traditionally relied on ingenious geometric optical designs and multiple feedback control systems, albeit at the cost of complexity. In this letter, a phase stability scheme for high‐resolution MDCS is proposed by replacing traditional laser sources with two highly coherent frequency combs. By employing dual‐comb interferometry, the phase distribution across a broad spectral range and the time information of all the excitation pulses are precisely measured, even in setups that lack phase stability. In the experiment, a rephasing MDCS of rubidium atoms is obtained by applying this approach, wherein the comb resolution is utilized to differentiate the couplings of hyperfine energy levels. This scheme simplifies the structure of MDCS and holds potential for applications in other MDCS systems involving many‐body interactions and non‐absorptive resonances.

Fully Phase-Locked Fiber Dual Comb Enables Accurate Frequency and Phase Detection in Multidimensional Coherent Spectroscopy

“…In the experimental scheme, the total phase fluctuations were mainly derived from the space optical path fluctuations between pulses A and B. We extracted the optical path fluctuations from the linear DCS signals and then this information was used to compensate for the phase fluctuations of echo [64,65]. After that, the SNR of the photon echo signal was improved to 435 by coherently averaging 177 times in the frequency domain, corresponding to a 1 s recording time, as shown in Figure 4b.…”