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arXiv · 2412.18438

Heterodyne coherent detection of the electric field temporal trace emitted by frequency-modulated comb lasers

Baptiste Chomet·Salim Basceken·Djamal Gacemi·Barbara Schneider·Mathias Beck·Angela Vasanelli·Benoît Darquié·Jérôme Faist·Carlo Sirtori
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Abstract

Frequency-modulated (FM) combs are produced by mode-locked lasers in which the electric field has a linearly chirped frequency and nearly constant amplitude. This regime of operation occurs naturally in certain laser systems and constitutes a valuable alternative to generate spectra with equidistant modes. Here, we use a low-noise fs-pulse comb as the local oscillator and combine dual comb heterodyne detection with time domain analysis of the multi-heterodyne signal to reveal the temporal trace of both amplitude and phase quadratures of FM comb lasers' electric field. This technique is applied to both a dense and a harmonic mid-infrared free-running quantum cascade laser frequency comb and shows direct evidence of the FM behavior together with the high degree of coherence of these sources. Our results furnish a deeper insight on the origin of the FM combs and pave the way to further improvement and optimization of these devices.

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Baptiste Chomet, Salim Basceken, Djamal Gacemi, Barbara Schneider, Mathias Beck, Angela Vasanelli, Benoît Darquié, Jérôme Faist, Carlo Sirtori. 2024-12-24. Heterodyne coherent detection of the electric field temporal trace emitted by frequency-modulated comb lasers. https://doi.org/10.1364/optica.525834

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