Dual‐Comb Femtosecond Solid‐State Laser with Inherent Polarization‐Multiplexing

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, 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 is demonstrated. Due to intracavity spatial separation of the orthogonally polarized beams, two sub‐100 fs pulse trains are simultaneously generated from a 1.05 µm Yb:CNGS (calcium niobium gallium silicate) 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 toward a new class of highly coherent, single‐cavity, dual‐comb laser sources operating in various spectral regions.

Emergent Phenomena of Vector Solitons Induced by the Linear Coupling

“…From another point of view, controlling the linear coupling can be utilized to create the polarization‐multiplexed dual comb, which has applications in sampling ultrafast phenomena. [ 83 ]…”

“…From another point of view, controlling the linear coupling can be utilized to create the polarization-multiplexed dual comb, which has applications in sampling ultrafast phenomena. [83] At the same pump power, by tuning the PC, the stable VS with a linear-coupling-induced asymmetric spectrum can be observed (Figure 7f). The pulses emit at the same repetition rate (Figure 7g), and there is only one pulse in the temporal domain (Figure 7h), demonstrating the synchronization of two modes.…”

Supplementary document for Dual-dispersion-regime dual-comb mode-locked laser - 5668364.pdf

“…The different pulse shaping mechanisms of the dual-dispersion dual-comb laser presented in the primary document may influence the relative noise characteristics compared to the original all-anomalous-dispersion dual-comb laser design of ref. [1]. In particular, it is unclear how the two setups compare in terms of common phase noise suppression relevant for mode-resolved dual-comb spectroscopy.…”

“…Here, the spectral overlap between the o-and e-beams around their respective peak wavelengths is significantly smaller when compared to ref. [1], which might have contributed to decreasing their gaincompetition-based cross-coupling. Additionally, by lengthening the duration of one of the pulses to the multi-picosecond range, we expect to have greatly suppressed intensity-dependent inter-pulse nonlinear interaction..…”

Dual-comb thin-disk oscillator

“…They rely on different effects to generate a repetition frequency offset between the two outputs. For example, polarization multiplexing in MIXSELs 15 , in bulk oscillators 16 and chromatic dispersion in a dual-wavelength fiber laser system 17 have been demonstrated. In bulk solid-state lasers, the directional dependence of the Kerr nonlinearity 18 , 19 was exploited.…”