Tri-comb spectroscopy

Multidimensional coherent spectroscopy (MDCS)(1,)(2) is a powerful method that enables the measurement of homogeneous linewidths in inhomogenously broadened systems, manybody interactions and coupling between excited resonances, all of which are not simultaneously accessible by any other method. Current implementations of MDCS require a bulky apparatus and suffer from resolution and acquisition speed limitations that constrain their applications outside the laboratory(3-5). Here, we propose and demonstrate an approach to nonlinear coherent spectroscopy that utilizes three slightly different repetition-rate frequency combs. Unlike traditional nonlinear methods, tri-comb spectroscopy uses only a single photodetector and no mechanical moving elements to enable faster acquisition times, while also providing comb resolution. As a proof of concept, a multidimensional coherent spectrum with comb cross-diagonal resolution is generated using only 365 ms of data. These improvements make MDCS relevant for systems with narrow resonances and it has the potential to be field deployable for chemical-sensing applications.