Electron-phonon relaxation rates and optical gain in a quantum cascade laser in a magnetic field

Radovanović, Jelena; Milanović, V.; Ikonić, Z.; Indjin, D.; Harrison, P.

doi:10.1063/1.1904706

Cited by 30 publications

(38 citation statements)

References 13 publications

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“…. As described in [31,34], all the states are assumed to be broadened with Gaussian-like energy distribution that depends on the magnetic field. The electron relaxation rates due to emission on LO phonons and IRS, are calculated by using equations (2) and (8).…”

Section: Numerical Resultsmentioning

confidence: 99%

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Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design

Daničić¹,

Radovanović

Milanović

et al. 2016

Physica E: Low-dimensional Systems and Nanostructures

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ReuseUnless indicated otherwise, fulltext items are protected by copyright with all rights reserved. The copyright exception in section 29 of the Copyright, Designs and Patents Act 1988 allows the making of a single copy solely for the purpose of non-commercial research or private study within the limits of fair dealing. The publisher or other rights-holder may allow further reproduction and re-use of this version -refer to the White Rose Research Online record for this item. Where records identify the publisher as the copyright holder, users can verify any specific terms of use on the publisher's website. TakedownIf you consider content in White Rose Research Online to be in breach of UK law, please notify us by emailing eprints@whiterose.ac.uk including the URL of the record and the reason for the withdrawal request. Abstract. We consider the influence of additional carrier confinement, achieved by application of strong perpendicular magnetic field, on inter Landau levels electron relaxation rates and the optical gain, of two different GaAs quantum cascade laser structures operating in the terahertz spectral range. Breaking of the in-plane energy dispersion and the formation of discrete energy levels is an efficient mechanism for eventual quenching of optical phonon emission and obtaining very long electronic lifetime in the relevant laser state. We employ our detailed model for calculating the electron relaxation rates (due to interface roughness and electron-longitudinal optical phonon scattering), and solve a full set of rate equations to evaluate the carrier distribution over Landau levels. The numerical simulations are performed for threeand four-well (per period) based structures that operate at 3.9THz and 1.9THz, respectively, both implemented in GaAs/Al0.15Ga0.85As. Numerical results are presented for magnetic field values from 1.5 T up to 20 T, while the band nonparabolicity is accounted for. Magnetic field effects on IntroductionQuantum Cascade Lasers (QCLs) have become important light sources for infrared spectroscopy within the last decade, especially when it comes to new structures operating in the terahertz (THz) region, suggesting numerous applications, such as chemical sensing, infrared imaging, non-invasive medical diagnostics and optical communications [1][2][3][4][5][6][7][8][9][10][11][12][13]. These devices are designed in such a manner so as to have electronic subbands defined as the upper and the lower laser level, electric pumping along the growth direction, as well as periodic repetition of active elements, which enhances the light amplification. Because of the specific properties of intersubband transitions, dynamical behavior is very different from that of inter-band lasers. The first and most important feature of intersubband transitions is very fast non-radiative scattering, proceeding on a time scale of few picoseconds [6]. THz frequencies belong to the quite under-utilized part of the electromagnetic spectrum, despite their significant application potential. This is mostly due to...

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Section: Numerical Resultsmentioning

confidence: 99%

“…The electron distribution over all LLs can be found by solving the nonlinear system of rate equations, which describe the change in levels populations as a difference between the rate at which carriers arrive and the rate at which they leave the subband under consideration [31]:…”

Section: Theoretical Considerationsmentioning

confidence: 99%

Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design

Daničić¹,

Radovanović

Milanović

et al. 2016

Physica E: Low-dimensional Systems and Nanostructures

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“…An intense magnetic field applied perpendicular to the 2DEG planes of a QCL causes two-dimensional continuous energy subbands to split into series of discrete Landau levels (LLs). Since the arrangement of Landau levels depends strongly on the magnitude of the magnetic field, this enables one to control the population inversion in the active region, and hence the optical gain [14][15][16][17]. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation.…”

Section: Introductionmentioning

confidence: 99%

Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range

et al. 2010

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We present a method for systematic optimization of quantum cascade laser active region, based on the use of the genetic algorithm. The method aims at obtaining a gain-maximized structure, designed to emit radiation at specified wavelengths suitable for direct absorption by pollutant gasses present in the ambient air. After the initial optimization stage, we introduce a strong external magnetic field to tune the laser output properties and to slightly modify the emission wavelength to match the absorption lines of additional compounds. The magnetic field is applied perpendicularly to the epitaxial layers, thus causing two-dimensional continuous energy subbands to split into series of discrete Landau levels. This affects all the relevant relaxation processes in the structure and consequently the lifetime of carriers in the upper laser level. Furthermore, strong effects of band nonparabolicity result in subtle changes of the lasing wavelength at magnetic fields which maximize the gain, thus providing a path for fine-tuning of the output radiation properties. Numerical results are presented for GaAs/Al x Ga 1−x As based quantum cascade laser structures designed to emit at particular wavelengths in the mid-infrared part of the spectrum.

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“…The highest operating temperature of 225K is reported for resonant-phonon design scheme assisted by external magnetic field for additional carrier confinement [3]. The role of the magnetic field is to suppress non-radiative intersubband relaxation processes and thus increase the optical gain [1,3,[8][9][10][11][12][13][14][15][16][17][18]. Hence, detailed understanding of various scattering mechanisms, * corresponding author; e-mail: radovanovic@etf.bg.ac.rs relevant for laser operation, may be an important factor in improving its performance.…”

Section: Introductionmentioning

confidence: 99%

Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser

et al. 2011

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We present a detailed analysis of GaAs/AlGaAs terahertz quantum cascade laser in the presence of an intense external magnetic field. One of the objectives in further development of THz quantum cascade laser is the realization of structures operating at higher temperatures. This is difficult to obtain as the operating photon emission energy is smaller than the longitudinal-optical phonon energy in the semiconductor material. With increased temperature, electrons in the upper radiative state gain sufficient in-plane energy to emit an longitudinal-optical phonon, which represents a non-radiative scattering and reduces the optical gain. By applying strong magnetic field, two-dimensional continuous energy subbands become split into series of discrete Landau levels, and at particular values of B it is possible to quench these non-radiative channels. Numerical simulations are performed on two-well design quantum cascade laser operating at 4.6 THz, implemented in GaAs/Al0.15Ga0.85As, and the magnetic field is perpendicular to the epitaxial layers. Strong oscillations of carrier lifetimes for the upper state of the laser transition, as a function of magnetic field are observed, which can be attributed to interface roughness scattering and longitudinal-optical phonon scattering between Landau levels.

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Electron-phonon relaxation rates and optical gain in a quantum cascade laser in a magnetic field

Cited by 30 publications

References 13 publications

Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design

Magnetic field effects on THz quantum cascade laser: A comparative analysis of three and four quantum well based active region design

Quantum Cascade Laser Design for Tunable Output at Characteristic Wavelengths in the Mid-Infrared Spectral Range

Inter-Landau Level Scattering Processes in Magnetic Field Assisted THz Quantum Cascade Laser

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