Adaptive real-time dual-comb spectroscopy

TLDR

Laser frequency combs provide coherent light with equally spaced sharp lines across a broad bandwidth, enabling high‑resolution molecular spectroscopy, yet dual‑comb spectroscopy remains limited by demanding high‑bandwidth servo‑control requirements. The study aims to overcome the servo‑control challenge in dual‑comb spectroscopy. The authors employ free‑running mode‑locked lasers and post‑processing, eliminating phase‑lock electronics and expert metrology. The technique was experimentally validated, showing that free‑running lasers and post‑processing enable real‑time dual‑comb spectroscopy with simplicity and versatility that could catalyze new molecular science discoveries.

Abstract

With the advent of laser frequency combs, coherent light sources that offer equally-spaced sharp lines over a broad spectral bandwidth have become available. One decade after revolutionizing optical frequency metrology, frequency combs hold much promise for significant advances in a growing number of applications including molecular spectroscopy. Despite its intriguing potential for the measurement of molecular spectra spanning tens of nanometers within tens of microseconds at Doppler-limited resolution, the development of dual-comb spectroscopy is hindered by the extremely demanding high-bandwidth servo-control conditions of the laser combs. Here we overcome this difficulty. We experimentally demonstrate a straightforward concept of real-time dual-comb spectroscopy, which only uses free-running mode-locked lasers without any phase-lock electronics, a posteriori data-processing, or the need for expertise in frequency metrology. The resulting simplicity and versatility of our new technique of adaptive dual-comb spectroscopy offer a powerful transdisciplinary instrument that may spark off new discoveries in molecular sciences.