June 2019
Spotlight Summary by Maurizio De Rosa
Pulses from a mid-infrared quantum cascade laser frequency comb using an external compressor
The observation of stable comb regimes does not always correspond to a train of regular pulses in the temporal domain. In particular, for quantum cascade lasers operating in the mid-infrared, the intrinsically short relaxation time between upper and lower laser levels makes it difficult to have intracavity isolated pulses when they operate in the comb regime. Instead, the emission is a strongly phase-modulated continuous field, still with a stable phase relationship between the different comb modes. This mode locking can be changed by externally compensating the intermodal phase differences, as shown for microresonator combs.
In this work, the authors demonstrate external compensation of the intermodal phase difference of the laser comb output by using a grating compressor. The compressor introduces a controlled group delay dispersion, which compensates for the intrinsic second-order dispersion of the lasing medium. In this way, they obtain a uniform train of 12-ps-short, high-peak power pulses from an initial phase-modulated continuous wave; the duration of the pulses is essentially limited by higher-order dispersion. This proof of concept opens the path to direct generation of short pulses in the mid-infrared in compact chip-scale devices.
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In this work, the authors demonstrate external compensation of the intermodal phase difference of the laser comb output by using a grating compressor. The compressor introduces a controlled group delay dispersion, which compensates for the intrinsic second-order dispersion of the lasing medium. In this way, they obtain a uniform train of 12-ps-short, high-peak power pulses from an initial phase-modulated continuous wave; the duration of the pulses is essentially limited by higher-order dispersion. This proof of concept opens the path to direct generation of short pulses in the mid-infrared in compact chip-scale devices.
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Article Information
Pulses from a mid-infrared quantum cascade laser frequency comb using an external compressor
Matthew Singleton, Mattias Beck, and Jérôme Faist
J. Opt. Soc. Am. B 36(6) 1676-1683 (2019) View: Abstract | HTML | PDF