Special Issue "Selected papers from “International Quantum Cascade Laser School and Workshop 2018”"

A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (31 October 2019).

Special Issue Editors

Prof. Sukhdeep Dhillon
Website
Guest Editor
Laboratoire Pierre Aigrain, Département de physique de l’ENS, École normale supérieure, PSL Research University, Université Paris Diderot, Sorbonne Paris Cité, Sorbonne Universités, UPMC Université Paris 06, CNRS, Paris, France
Interests: optoelectronics; photonics; terahertz; mid-infrared; ultrafast spectroscopy; nonlinear optics
Dr. Sushil Kumar
Website
Guest Editor
Department of Electrical and Computer Engineering, Lehigh University, Bethlehem, PA, 18015, USA
Prof. Angela Vasanelli
Website
Guest Editor
Université Paris Diderot-Paris7, Laboratoire Matériaux et Phénomènes Quantiques, Bâtiment Condorcet, Case courrier 7021, F-75205 PARIS CEDEX 13 France

Special Issue Information

Dear Colleagues,

IQCLSW 2018 will be the 8th conference in a series of international meetings on quantum cascade lasers (QCLs), and will be held in Cassis (France), 2–7 September, 2018. QCLs are unipolar optoelectronic devices that exploit optical transitions between engineered electronic subbands in semiconductor quantum wells. This concept has provided outstanding laser performance across the mid-infrared and terahertz (THz) spectral ranges, where there is a lack of practical photonic sources. IQCLSW is the main biennial event for the QCL community, divided into a school and workshop environment. The school provides an overview of the main developments and concepts in the field through courses from world leading researchers in the domain. The second workshop part presents the latest developments in the community, from fundamental physics to the exploitation and applications of this technology.

We are very glad to serve as Guest Editors of this Special Issue to be published in Photonics that will contain a selection of papers submitted and accepted at IQCLSW 2018. Its main scope is to provide a timely and broad collection of the most innovative topics discussed at the latest edition of the school and workshop related to mid-infrared and THz photonics and optoelectronics. We warmly invite researchers to submit their contributions to this Special Issue. Potential topics include, but are not limited to:

  • Theory and design of quantum cascade lasers
  • New breakthroughs in quantum cascade laser performance
  • Novel and new material systems
  • Nonlinear effects in quantum cascade lasers
  • Broadband gain media design and growth
  • Quantum cascade laser photonic integrated circuits
  • Novel waveguides for functionalised emission
  • Strong light-matter interactions
  • New detection schemes and methods (coherent detection, near-field etc.)
  • Chemical/biomedical applications for cascade lasers
  • Communication applications for cascade lasers
  • Active imaging applications for cascade lasers
  • Defense/homeland security applications for cascade lasers

Please note that for this Special Issue on the IQCLSW, MDPI will waive the Article Processing Charges (APC) for submissions from this conference.

Prof. Sukhdeep Dhillon
Dr. Sushil Kumar
Prof. Angela Vasanelli
Guest Editor

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Photonics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Quantum Cascade Lasers
  • Mid-infrared and Terahertz Photonics
  • Novel optical effects
  • Quantum and Waveguide Engineering
  • Light-matter interactions
  • New material systems
  • Quantum Electronics
  • Semiconductor Lasers

Published Papers (6 papers)

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Research

Open AccessArticle
Quantum Theory of Multisubband Plasmon– Phonon Coupling
Photonics 2020, 7(1), 19; https://doi.org/10.3390/photonics7010019 - 20 Feb 2020
Abstract
We present a theoretical description of the coupling between longitudinal optical phonons and collective excitations of a two-dimensional electron gas. By diagonalizing the Hamiltonian of the system, including Coulomb electron–electron and Fröhlich interactions, we observe the formation of multisubband polarons, mixed states partially [...] Read more.
We present a theoretical description of the coupling between longitudinal optical phonons and collective excitations of a two-dimensional electron gas. By diagonalizing the Hamiltonian of the system, including Coulomb electron–electron and Fröhlich interactions, we observe the formation of multisubband polarons, mixed states partially phonon and partially multisubband plasmon, characterized by a coupling energy which is a significant fraction, up to 40 % , of the phonon energy. We demonstrate that multisubband plasmons and longitudinal optical phonons are in the ultra-strong coupling regime in several III–V and II–VI material systems. Full article
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Open AccessEditor’s ChoiceArticle
RF Injection of THz QCL Combs at 80 K Emitting over 700 GHz Spectral Bandwidth
Photonics 2020, 7(1), 9; https://doi.org/10.3390/photonics7010009 - 16 Jan 2020
Cited by 1
Abstract
We report about RF injection locking of an homogeneous THz quantum cascade laser operating at 3 THz central frequency. The extremely diagonal nature of the optical transition, combined with low-loss copper-based double-metal waveguides, allow CW operation up to 105 K and CW power [...] Read more.
We report about RF injection locking of an homogeneous THz quantum cascade laser operating at 3 THz central frequency. The extremely diagonal nature of the optical transition, combined with low-loss copper-based double-metal waveguides, allow CW operation up to 105 K and CW power in excess of 5.6 mW measured at 80 K. Terahertz emission spanning up to 600 GHz, together with a narrow beatnote, indicate comb operation at 80 K, and strong RF injection clearly modifies the laser spectrum up to 700 GHz spectral bandwidth making these devices ideal candidates for an on-chip dual comb spectrometer. Full article
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Open AccessArticle
Short Barriers for Lowering Current-Density in Terahertz Quantum Cascade Lasers
Photonics 2020, 7(1), 7; https://doi.org/10.3390/photonics7010007 - 08 Jan 2020
Cited by 3
Abstract
Scattering due to interface-roughness (IR) and longitudinal-optical (LO) phonons are primary transport mechanisms in terahertz quantum-cascade lasers (QCLs). By choosing GaAs/Al0.10Ga0.90As heterostructures with short-barriers, the effect of IR scattering is mitigated, leading to low operating current-densities. A series of [...] Read more.
Scattering due to interface-roughness (IR) and longitudinal-optical (LO) phonons are primary transport mechanisms in terahertz quantum-cascade lasers (QCLs). By choosing GaAs/Al0.10Ga0.90As heterostructures with short-barriers, the effect of IR scattering is mitigated, leading to low operating current-densities. A series of resonant-phonon terahertz QCLs developed over time, achieving some of the lowest threshold and peak current-densities among published terahertz QCLs with maximum operating temperatures above 100 K. The best result is obtained for a three-well 3.1 THz QCL with threshold and peak current-densities of 134 A/cm2 and 208 A/cm2 respectively at 53 K, and a maximum lasing temperature of 135 K. Another three-well QCL designed for broadband bidirectional operation achieved lasing in a combined frequency range of 3.1–3.7 THz operating under both positive and negative polarities, with an operating current-density range of 167–322 A/cm2 at 53 K and maximum lasing temperature of 141 K or 121 K depending on the polarity of the applied bias. By showing results from QCLs developed over a period of time, here we show conclusively that short-barrier terahertz QCLs are effective in achieving low current-density operation at the cost of a reduction in peak temperature performance. Full article
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Open AccessFeature PaperArticle
Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models
Photonics 2020, 7(1), 2; https://doi.org/10.3390/photonics7010002 - 18 Dec 2019
Cited by 3
Abstract
n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe [...] Read more.
n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3. Full article
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Open AccessArticle
Evidence of Intersubband Linewidth Narrowing Using Growth Interruption Technique
Photonics 2019, 6(2), 38; https://doi.org/10.3390/photonics6020038 - 01 Apr 2019
Cited by 1
Abstract
We report on the systematic study of two main scattering mechanisms on intersubband transitions, namely ionized impurity scattering and interface roughness scattering. The former mechanism has been investigated as a function of the dopants position within a multiple GaAs/AlGaAs quantum well structure and [...] Read more.
We report on the systematic study of two main scattering mechanisms on intersubband transitions, namely ionized impurity scattering and interface roughness scattering. The former mechanism has been investigated as a function of the dopants position within a multiple GaAs/AlGaAs quantum well structure and compared to the transition of an undoped sample. The study on the latter scattering mechanism has been conducted using the growth interruption technique. We report an improvement of the intersubband (ISB) transition linewidth up to 11% by interrupting growth at GaAs-on-AlGaAs interfaces. As a result, the lifetime of intersubband polaritons could be improved up to 9%. This leads to a reduction of 17% of the theoretical threshold intensity for polaritonic coherent emission. This work brings a useful contribution towards the realization of polariton-based devices. Full article
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Open AccessEditor’s ChoiceArticle
Long Wavelength (λ > 17 µm) Distributed Feedback Quantum Cascade Lasers Operating in a Continuous Wave at Room Temperature
Photonics 2019, 6(1), 31; https://doi.org/10.3390/photonics6010031 - 21 Mar 2019
Cited by 5
Abstract
The extension of the available spectral range covered by quantum cascade lasers (QCL) would allow one to address new molecular spectroscopy applications, in particular in the long wavelength domain of the mid-infrared. We report in this paper the realization of distributed feedback (DFB) [...] Read more.
The extension of the available spectral range covered by quantum cascade lasers (QCL) would allow one to address new molecular spectroscopy applications, in particular in the long wavelength domain of the mid-infrared. We report in this paper the realization of distributed feedback (DFB) QCLs, made of InAs and AlSb, that demonstrated a continuous wave (CW) and a single mode emission at a wavelength of 17.7 µm, with output powers in the mW range. This is the longest wavelength for DFB QCLs, and for any QCLs or semiconductor lasers in general, operating in a CW at room temperature. Full article
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