Microscopic approach to second harmonic generation in quantum cascade lasers

Winge, David O.; Lindskog, M.; Wacker, Andreas

doi:10.1364/oe.22.018389

Cited by 7 publications

(7 citation statements)

References 41 publications

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“…41 In this context, we note that the gain saturation, defining the simulated intensity I sim , contains backwards traveling waves, which do not contribute to the experimental output as discussed in Ref. 56. Thus, I sim is expected to overestimate the output by a factor up to two for low transmittivity.…”

Section: Methodsmentioning

confidence: 86%

Simulating terahertz quantum cascade lasers: Trends from samples from different labs

Winge

Franckié

Wacker

2016

Journal of Applied Physics

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We present a systematic comparison of the results from our non-equilibrium Green's function formalism with a large number of AlGaAs-GaAs terahertz quantum cascade lasers previously published in the literature. Employing identical material and simulation parameters for all samples, we observe that discrepancies between measured and calculated peak currents are similar for samples from a given group. This suggests that the differences between experiment and theory are partly due to a lacking reproducibility for devices fabricated at different laboratories. Varying the interface roughness height for different devices, we find that the peak current under lasing operation hardly changes, so that differences in interface quality appear not to be the sole reason for the lacking reproducibility.

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Section: Methodsmentioning

confidence: 86%

Simulating terahertz quantum cascade lasers: Trends from samples from different labs

Winge

Franckié

Wacker

2016

Journal of Applied Physics

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“…13,17 In the NEGF model, gain is calculated from the dynamical conductance, and calculations in a strong ac field follow the procedure outlined in Ref. 18.…”

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confidence: 99%

Comparative analysis of quantum cascade laser modeling based on density matrices and non-equilibrium Green's functions

Lindskog

Wolf

Trinité

et al. 2014

Applied Physics Letters

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We study the operation of an 8.5 µm quantum cascade laser based on GaInAs/AlInAs lattice matched to InP using three different simulation models based on density matrix (DM) and nonequilibrium Green's function (NEGF) formulations. The latter advanced scheme serves as a validation for the simpler DM schemes and, at the same time, provides additional insight, such as the temperatures of the sub-band carrier distributions. We find that for the particular quantum cascade laser studied here, the behavior is well described by simple quantum mechanical estimates based on Fermi's golden rule. As a consequence, the DM model, which includes second order currents, agrees well with the NEGF results. Both these simulations are in accordance with previously reported data and a second regrown device

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“…Our model, without electron-electron scattering has been previously tested successfully on superlattices and QCL heterostructures [12,21,22]. The case considered here is a QCL design from 2009 [23].…”

Section: Resultsmentioning

confidence: 99%

Simple electron-electron scattering in non-equilibrium Green's function simulations

Winge

Franckié

Verdozzi

et al. 2016

J. Phys.: Conf. Ser.

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Abstract. In this work we include electron-electron interaction beyond Hartree-Fock level in our non-equilibrium Green's function approach by a crude form of GW through the Single Plasmon Pole Approximation. This is achieved by treating all conduction band electrons as a single effective band screening the Coulomb potential. We describe the corresponding self-energies in this scheme for a multi-subband system. In order to apply the formalism to heterostructures we discuss the screening and plasmon dispersion in both 2D and 3D systems. Results are shown for a four well quantum cascade laser with different doping concentration where comparisons to experimental findings can be made. IntroductionSince the quantum cascade laser (QCL) was introduced more than 20 years ago [1] it has continuously been improved and redesigned to operate from the mid-infrared all the way down to the Terahertz (THz) range. Compact laser sources at these wavelengths are valuable for spectroscopic applications [2] but a major problem is that THz QCLs do not operate at room temperature. This can be overcome via difference frequency generation which recently has been demonstrated at powers in the milli-watt range [3]. Direct THz-QCLs still generate a lot of interest in the research community due to the promise of higher wall-plug efficiency and the prospects of miniaturization of cryo-coolers.The main temperature degrading mechanism of the THz QCLs is currently not fully understood and is still debated by the community [4]. This is a challenge to theory and there is a great need of realistic modeling tools that are able to treat all important quantum effects on the same footing. A summary of different methods for simulating these structures is found in [5]. Monte Carlo simulations have shown that electron-electron interaction, beyond the meanfield or Hartree approximation can influence the dynamics of THz QCLs [6,7,8].In this work we include and study the effects of a simple electron-electron scattering via the Single Plasmon Pole Approximation (SPPA) [9,10]. In this approximation we capture both the static limit as well as dynamic effects. This gives an energy dependent (non-local in time) interaction beyond the Hartree-Fock approximation. This has been studied in a similar model with promising results [11], and with this work we want to adapt the idea into our model described in Ref. [12]. In other methods based on Non-Equilibrium Green's Functions (NEGF)

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Microscopic approach to second harmonic generation in quantum cascade lasers

Cited by 7 publications

References 41 publications

Simulating terahertz quantum cascade lasers: Trends from samples from different labs

Simulating terahertz quantum cascade lasers: Trends from samples from different labs

Comparative analysis of quantum cascade laser modeling based on density matrices and non-equilibrium Green's functions

Simple electron-electron scattering in non-equilibrium Green's function simulations

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