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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Frequency Comb Generation at 2 μm with Electro-Optic Modulators for Spectroscopic Applications
摘要： Mid-infrared (2–20 μm) gas sensing allows the detection of strong molecular absorptions with rather small absorption lengths (≤1 m). Various techniques can perform spectroscopic measurements in the mid-infrared but dual-comb spectroscopy (DCS) is one of the most powerful knowing its precision and real-time abilities [1]. However, setups used to perform DCS are in general complex since they require the phase locking of two independent femtosecond lasers at the known state of the art stability. This particular drawback can be bypassed if the combs are generated with electro-optic modulators (EOM) [2]. However, these equipments operate in the telecommunication wavelengths, generally near 1.55 μm where molecular absorptions are not very intense. Here, we experimentally demonstrate two different techniques of generating frequency combs with EOMs around 2 μm.
关键词： Spectroscopic applications,Frequency comb generation,Mid-infrared,Electro-optic modulators,Dual-comb spectroscopy
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Computational High-Resolution Dual-Comb Spectroscopy with a Free-Running All-Fiber Laser
摘要： Dual-comb spectroscopy (DCS) has experienced a remarkable growth propelled by recent advances in fiber and semiconductor technology. A key enabler for DCS is mutual stability between two repetition-rate-mismatched frequency combs, which conventionally relies on feedback loops employing additional optics and electronics to synchronize a pair of sources. This limitation can be overcome in several ways, of which one of the most promising is the generation of two frequency combs in a single free-running fiber laser cavity [1–3]. To date, however, the only configuration proven to be compatible with Doppler-limited spectroscopy was the dual-color laser presented in Ref. [2] requiring external spectral broadening, thus adding an extra layer of complexity. Here, we report on the realization of a drastically simplified all-fiber dual-comb laser (AFDCL) with an unprecedentedly low number of components and battery-operation-compatible electrical power consumption (0.35 W) with excellent suitability for spectroscopy of Doppler-limited transitions (Fig. 1). A key feature of our solution relying on polarization-multiplexing [3] is that the laser cavity has an easily adjustable repetition rate difference ranging from sub-kHz to dozens of kHz obtained by varying the intracavity polarization state using polarization controllers (PC) and/or the length of the polarization maintaining fiber in the cavity, which is not possible in the dual-color or bidirectional schemes. Furthermore, we achieve uninterrupted operation times of dozens of hours, and a record-high repetition rate for an AFDCL exceeding 140 MHz to maximize the optical power per comb tooth. High-resolution molecular dual-comb spectroscopy in free-running mode is made possible thanks to a novel real-time compatible phase correction algorithm that marks a radical departure from the cross-correlation or cross-ambiguity function paradigm, hence considerably lowering the complexity of such procedures. As a demonstration, we measure P18-P27 lines of the 2ν3 band of H13C14N at 10 Torr with FWHM Doppler line widths of ~450 MHz within 200 ms (Fig. 1b,c) with better than 1% of precision in a 1 THz bandwidth.
关键词： high-resolution,free-running,molecular spectroscopy,Dual-comb spectroscopy,all-fiber laser
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - All-Polarization-Maintaining Dual-Color/Dual-Comb Yb:Fiber Laser
摘要： Dual-comb spectroscopy systems based on two pulse trains emitted from a single laser cavity benefit from passive mutual coherence between the two pulse trains, which leads to common-mode noise cancellation in the down converted radio-frequency (RF)-comb [1]. Due to their robustness, single cavity dual-color/dual-comb fiber lasers are promising candidates for such spectroscopy systems [2,3]. Here, we present a novel method to generate two pulse trains out of a single fiber laser cavity based on mechanical spectral filtering, which offers two key features: dynamical adjustment of the spectral separation between the two pulse trains and tuning of the difference in repetition rates. After demonstrating the concept in a 23-MHz nonlinear polarization evolution (NPE) mode-locked ytterbium (Yb) laser [4], we have now for the first time implemented this concept in a nonlinear amplified loop mirror (NALM) mode-locked all-polarization maintaining (PM) Yb:fiber laser operating at a repetition rate of 77 MHz, thus improving both the stability as well as the non-aliasing dual-comb bandwidth. The laser contains a free-space arm with a transmission grating compressor, in which the spectral components of the intra-cavity light are spatially dispersed (Fig.1(a)). By introducing a small beam block into the grating compressor, we split the spectrum into two separate regions. We show that these two spectral regions can be independently mode-locked, thus creating two pulse trains with slightly different repetition rates (Fig.1(b-d)). Due to the spatial distribution of the spectral components, we can vary the width of the spectral cut between the two spectra by rotating the beam block (Fig. 1(b), blue curves). Furthermore, adjusting the grating spacing (and thus the amount of dispersion) allows us to tune the difference in the repetition rate ?frep from 1-6 kHz (Fig. 1(e)). After spectral separation at the cavity output, the pulse centered around 1030 nm is amplified and broadened in a nonlinear fiber to create a spectral overlap with the 1060 nm-pulse (Fig. 1(f)). The overlapping spectrum is bandpass-filtered around 1055 nm and sent onto a photodiode (PD). An oscilloscope trace of the PD output shows interferograms (Fig. 1(f), inset) occurring with a periodicity of 1/?frep, which correspond to the Fourier-transform of the down-converted RF comb that is generated by the beating of both optical combs.
关键词： repetition rate tuning,polarization maintaining,Yb:fiber laser,spectral filtering,Dual-comb spectroscopy
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - High-Power Dual-Comb Thin-Disk Oscillator
摘要： Dual-comb spectroscopy is a rapidly advancing spectrometric technique where the temporal interferograms generated with two asynchronous trains of pulses are recorded, and Fourier transformed to reveal the spectrum of an absorber in the beam path [1]. To date, best performance is achieved with systems involving complex active stabilization of two femtosecond erbium fiber lasers [1]. One way to simplify the technique is to generate a dual-comb output from a single laser cavity. However, there have been only a few demonstrations of such a scheme so far [2,3]. Here we present a dual-comb system based on a single thin-disk oscillator. The novel architecture effectively rejects common noise, with mutual coherence time exceeding one second without any active stabilization. Moreover, the system shows nearly an order of magnitude higher average and peak output powers compared to previous dual-comb demonstrations. Efficient nonlinear frequency conversion to the UV or mid-IR regions—of high interest to molecular spectroscopy—will thus be greatly facilitated.
关键词： thin-disk oscillator,high-power,Yb:YAG,Kerr-lens mode-locked,dual-comb spectroscopy
更新于2025-09-11 14:15:04