Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques

Jumpertz, Louise; Michel, Florian; Pawlus, Robert; Elsäßer, Wolfgang; Schires, Kevin; Carras, Mathieu; Grillot, Frédéric

doi:10.1063/1.4940767

Cited by 47 publications

(14 citation statements)

References 32 publications

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“…The LBF in semiconductor lasers describes the phase-amplitude coupling effects of the refractive index and the gain, which enhances the low-frequency FN and thereby broadens the spectral linewidth [45]. Owing to the nearly symmetric homogeneous gain broadening of the intersubband transition, QCLs operating below the lasing threshold usually show near-zero LBFs [46], while QCLs operating above threshold show higher values ranging from 0.2 to 3.0 [47][48][49]. The non-zero LBF in QCLs has been attributed to the non-parabolicity of the band structure, the many-body effects, the resonant tunneling transport, and the counter-rotating wave contribution [50,51].…”

Section: Resultsmentioning

confidence: 99%

Rate equation modeling of the frequency noise and the intrinsic spectral linewidth in quantum cascade lasers

Wang

Grillot

2018

Opt. Express

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This work theoretically investigates the frequency noise (FN) characteristics of quantum cascade lasers (QCLs) through a three-level rate equation model, which takes into account both the carrier noise and the spontaneous emission noise through the Langevin approach. It is found that the power spectral density of the FN exhibits a broad peak due to the carrier noise induced carrier variation in the upper laser level, which is enhanced by the stimulated emission process. The peak amplitude is strongly dependent on the gain stage number and the linewidth broadening factor. In addition, an analytical formula of the intrinsic spectral linewidth of QCLs is derived based on the FN analysis. It is demonstrated that the laser linewidth can be narrowed by reducing the gain coefficient and/or accelerating the carrier scattering rates of the upper and the lower laser levels.

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Section: Resultsmentioning

confidence: 99%

Rate equation modeling of the frequency noise and the intrinsic spectral linewidth in quantum cascade lasers

Wang

Grillot

2018

Opt. Express

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“…The standard deviation of the measurements does not exceed 15%, and the measured values are in good agreement with those obtained using the standard Hakki-Paoli method. The proposed technique may be of prime importance for advanced types of laser devices, such as quantum cascade lasers 38 39 40 and lasers on silicon 41 42 , for which the LBF behavior does require a better understanding and vivid discussions dealing with the thermal effects still persist.…”

Section: Resultsmentioning

confidence: 99%

Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking

Wang

Schires

Osiński

et al. 2016

Sci Rep

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In semiconductor lasers, current injection not only provides the optical gain, but also induces variation of the refractive index, as governed by the Kramers-Krönig relation. The linear coupling between the changes of the effective refractive index and the modal gain is described by the linewidth broadening factor, which is responsible for many static and dynamic features of semiconductor lasers. Intensive efforts have been made to characterize this factor in the past three decades. In this paper, we propose a simple, flexible technique for measuring the linewidth broadening factor of semiconductor lasers. It relies on the stable optical injection locking of semiconductor lasers, and the linewidth broadening factor is extracted from the residual side-modes, which are supported by the amplified spontaneous emission. This new technique has great advantages of insensitivity to thermal effects, the bias current, and the choice of injection-locked mode. In addition, it does not require the explicit knowledge of optical injection conditions, including the injection strength and the frequency detuning. The standard deviation of the measurements is less than 15%.

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“…factor (more commonly called the α-factor) of such lasers were also carried out. The retrieved above-threshold value of the effective α-factor is in the order of 2 whereas for currents below threshold, it is in the order of -0.4 [29], [30]. This relatively large enhancement of the linewidth enhancement factor can be attributed to the QCLs operation far above the threshold current and to the distributed feedback grating cavity which can induce severe longitudinal spatial hole burning [31].…”

Section: A Devicesmentioning

confidence: 97%

Investigation of Chaotic and Spiking Dynamics in Mid-Infrared Quantum Cascade Lasers Operating Continuous-Waves and Under Current Modulation

Spitz

Herdt

et al. 2019

IEEE J. Select. Topics Quantum Electron.

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This study investigates chaotic and spiking dynamics of mid-infrared quantum cascade lasers operating under external optical feedback and emitting at 5.5 µm and 9 µm. In order to deepen the understanding, the route to chaos is experimentally studied in the case of continuous-wave and current modulation operation. The non-linear dynamics are analyzed with bifurcation diagrams. While for quasi-continuous wave operation, chaos is found to be more complex, pure continuous wave pumping always leads to the generation of a regular spiking induced lowfrequency fluctuations dynamics. In the latter, results show that by combining external optical feedback with periodic forcing and further induced current modulation allows a better control of the chaotic dropouts. This work provides a novel insight into the development of future secure free-space communications based on quantum cascade lasers or unpredictable optical countermeasure systems operating within the two transparency atmospheric windows hence between 3 µm-5 µm and 8.5 µm-11 µm.

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Measurements of the linewidth enhancement factor of mid-infrared quantum cascade lasers by different optical feedback techniques

Cited by 47 publications

References 32 publications

Rate equation modeling of the frequency noise and the intrinsic spectral linewidth in quantum cascade lasers

Rate equation modeling of the frequency noise and the intrinsic spectral linewidth in quantum cascade lasers

Thermally insensitive determination of the linewidth broadening factor in nanostructured semiconductor lasers using optical injection locking

Investigation of Chaotic and Spiking Dynamics in Mid-Infrared Quantum Cascade Lasers Operating Continuous-Waves and Under Current Modulation

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