Femtosecond pulses from a mid-infrared quantum cascade laser

Täschler, Philipp; Bertrand, Mathieu; Schneider, Barbara; Singleton, Matthew; Jouy, Pierre; Kapsalidis, Filippos; Beck, Mattias; Faist, Jérôme

doi:10.1038/s41566-021-00894-9

Cited by 57 publications

(28 citation statements)

References 43 publications

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“…In contrast, considering the relatively smaller GVD of the optimised designs, appropriate dispersion engineering would ensure the same sign of the GVD over the whole comb range. This, together with the fact that the simulated FWM nonlinearity has the same sign over the range where the gain is flat, should mitigate the commonly observed two-lobed spectra [2,3,[6][7][8] and enable mid-infrared frequency combs with more even intensity over the whole gain spectrum.…”

Section: Optimization Of Flat and Broad Gain At 6 µMmentioning

confidence: 84%

“…However, this often neglects the dispersion coming from the active medium, which can be significant. As a result, frequency combs often feature spectral holes [2,3,[5][6][7][8] or do not span the gain bandwidth, since the group velocity delay (GVD) cannot compensate the self-phase modulation shift. In order to achieve a broader comb operation, it is therefore important to achieve a low dispersion and broad, flat, gain profile.…”

Section: Introductionmentioning

confidence: 99%

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Optimization of broad gain and high optical nonlinearity of mid-infrared quantum cascade laser frequency combs

Franckié¹

2022

Preprint

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Mid-infrared Quantum Cascade Lasers (QCLs) are compact and efficient sources ideal for molecular spectroscopy applications, such as dual-comb spectroscopy. However, despite over a decade of active developments of QCL frequency comb devices, their bandwidth is limited to around 100 cm −1 , severely limiting their application for multi-gas, liquid, and solid sensing. Even though very broad gain QCLs have been presented, these were not able to improve the comb bandwidth, whose main limitations are variations of the gain and dispersion with frequency. A perfectly flat gain spectrum would mitigate this, as the dispersion as well as the parametric gain necessary to overcome the losses at gain clamping, vanishes. On the other hand, comb formation rests on four-wave mixing, a third-order nonlinear process, which is very strong in QCLs. Due to the subband nature of these devices, this nonlinearity can be designed and enhanced in order to facilitate comb formation. In this work, we present optimised designs with broad and flat-top gain spectra spanning as much as 220 cm −1 , as well as up to 30 times stronger FWM nonlinearity than a typical bound-to-continuum QCL design. The optimisation utilises a nonequilibriumn Green's function model with high predictive power, and obeys constraints on gain and current density, ensuring efficient devices. Such high nonlinearity in combination with a moderate, saturable gain, could allow for non-classical light generation in QCLs. On the other hand, doubling the spectral bandwidth of QCL combs would be a large step towards high-speed spectroscopy of complex gas mixtures and liquids.

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Section: Optimization Of Flat and Broad Gain At 6 µMmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Optimization of broad gain and high optical nonlinearity of mid-infrared quantum cascade laser frequency combs

Franckié¹

2022

Preprint

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“…Furthermore, mode-locking is hard to be realized in QCLs due to their picosecond-level gain recovery time. The picosecond-level laser pulse at 8 µm was only recently, in 2020, achieved in QCLs [49], and femtosecond pulses were generated via spectral filtering, gain modulation-induced spectral broadening, and external pulse compression in 2021 [50].…”

Section: Methods For Mid-infrared Generation Technologymentioning

confidence: 99%

Generation of 8–20 μm Mid-Infrared Ultrashort Femtosecond Laser Pulses via Difference Frequency Generation

Zhu

Wang

et al. 2022

Photonics

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Mid-infrared (MIR) ultrashort laser pulses have a wide range of applications in the fields of environmental monitoring, laser medicine, food quality control, strong-field physics, attosecond science, and some other aspects. Recent years have seen great developments in MIR laser technologies. Traditional solid-state and fiber lasers focus on the research of the short-wavelength MIR region. However, due to the limitation of the gain medium, they still cannot cover the long-wavelength region from 8 to 20 µm. This paper summarizes the developments of 8–20 μm MIR ultrafast laser generation via difference frequency generation (DFG) and reviews related theoretical models. Finally, the feasibility of MIR power scaling by nonlinear-amplification DFG and methods for measuring the power of DFG-based MIR are analyzed from the author’s perspective.

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“…Earlier in the article, the effects associated with smooth pulse envelopes were studied in detail. In reality, measurements of pulse envelopes rarely show any smooth front shape far from the maximum of the envelope [15,19,20]. In this subsection, we consider the dynamics of ionization under the action of a pulse with a weaker prepulse, the envelope of which is given by…”

Section: Presence Of a Prepulsementioning

confidence: 99%

Dynamics of Gas Ionization by Laser Pulses with Different Envelope Shapes

2023

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The properties of the dynamics of gas ionization under the action of femtosecond ionizing laser pulses with various envelope shapes are studied. It is shown that the duration of ionization in the saturation regime (at a high final degree of ionization) can either increase or decrease with an increase in the peak intensity of the ionizing pulse, depending on the shape of its envelope. We also determined the influence of the pulse shape on the spectrum of Brunel harmonics and the terahertz yield when two-color pulses are used.

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Femtosecond pulses from a mid-infrared quantum cascade laser

Cited by 57 publications

References 43 publications

Optimization of broad gain and high optical nonlinearity of mid-infrared quantum cascade laser frequency combs

Optimization of broad gain and high optical nonlinearity of mid-infrared quantum cascade laser frequency combs

Generation of 8–20 μm Mid-Infrared Ultrashort Femtosecond Laser Pulses via Difference Frequency Generation

Dynamics of Gas Ionization by Laser Pulses with Different Envelope Shapes

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