Dual-comb femtosecond solid-state laser with inherent polarization-multiplexing

TL;DR

This paper introduces a novel dual-comb laser using polarization-multiplexing in a single cavity, achieving ultra-low noise and enabling high-precision, free-running spectroscopic measurements without stabilization.

Contribution

It presents a new dual-comb generation method from a single solid-state laser cavity utilizing intrinsic polarization-multiplexing, reducing noise and broadening applications.

Findings

Achieved the lowest relative noise for bulk dual-comb sources.

Generated two orthogonally-polarized pulse trains simultaneously.

Supported free-running mode-resolved spectroscopy over a second.

Abstract

Dual-comb spectroscopy is a rapidly developing technique enabling ultraprecise broadband optical diagnostics of atoms and molecules. This powerful tool typically requires two phase-locked femtosecond lasers, yet it has been shown that it can be realized without any stabilization if the combs are generated from a single laser cavity. Still, unavoidable intrinsic relative phase-fluctuations always set a limit on the precision of any spectroscopic measurements, hitherto limiting the applicability of bulk dual-comb lasers for mode-resolved studies. Here, we demonstrate a versatile concept for low-noise dual-comb generation from a single-cavity femtosecond solid-state laser based on intrinsic polarization-multiplexing inside an optically anisotropic gain crystal. Due to intracavity spatial separation of the orthogonally-polarized beams, two sub-100 fs pulse trains are simultaneously generated from a 1.05 $\mu$m Yb:CNGS oscillator with a repetition rate difference of 4.7 kHz. The laser exhibits the lowest relative noise ever demonstrated for a bulk dual-comb source, supporting free-running mode-resolved spectroscopic measurements over a second. Moreover, the developed dual-comb generation technique can be applied to any solid-state laser exploiting a birefringent active crystal, paving the way towards a new class of highly-coherent, single-cavity, dual-comb laser sources operating in various spectral regions.