Comparison of THz-QCL Designs Supporting Clean N-Level Systems

Three different Terahertz quantum-cascade-laser designs supporting clean n-level systems were analyzed using nonequilibrium Green’s functions. In clean n-level systems, most of the electrons occupy the active laser levels, with thermally activated leakage channels being suppressed almost entirely up to room temperature. Simulations of the three designs, namely a resonant phonon design, a two-well design, and a split-well direct-phonon design were investigated. The results from the simulations indicated that the two-well design would perform best overall, in terms of variations in current density, interface roughness, and ionized impurity scattering. We conclude that future research aiming to improve the temperature performance of such laser designs should be based on a two-well design.

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The Effect of Doping in Split-Well Direct-Phonon THz Quantum-Cascade Laser Structures

Photonics ◽

10.3390/photonics8060195 ◽

2021 ◽

Vol 8 (6) ◽

pp. 195

Author(s):

Nathalie Lander Gower ◽

Silvia Piperno ◽

Asaf Albo

Keyword(s):

Quantum Cascade Laser ◽

Impurity Scattering ◽

Level System ◽

Quantum Cascade ◽

N Level ◽

Temperature Performance ◽

Ionized Impurity Scattering ◽

In Doping ◽

Positive Effect ◽

Effect Of Doping

We have studied the effect of doping on the temperature performance of a split-well (SW) direct-phonon (DP) terahertz (THz) quantum-cascade laser (QCL) scheme supporting a clean three-level system. Achieving a system that is as close as possible to a clean n-level system proved to be the strategy that led to the best temperature performance in THz-QCLs. We expected to obtain a similar improvement to that observed in resonant-phonon (RP) schemes after increasing the carrier concentration from 3 × 1010 cm−2 to 6 × 1010 cm−2. Our goal was to improve the temperature performance by increasing the doping, ideally the results should have improved. To our surprise, in the devices we checked, the results show the contrary. Although an increase in doping had previously shown a positive effect in RP schemes, our results indicated that this does not happen with SW–DP devices. However, we observed a significant increase in gain broadening and a reduction in the dephasing time as the doping and temperature increased. We attribute these effects to enhanced ionized-impurity scattering (IIS). The observation and study of effects related to dephasing included in our experimental work have previously only been possible via simulation.

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High photoresponse in room-temperature quantum cascade detectors based on a coupled-well design

10.1117/12.2250468 ◽

2017 ◽

Author(s):

T. Dougakiuchi ◽

K. Fujita ◽

T. Hirohata ◽

A. Ito ◽

M. Hitaka ◽

...

Keyword(s):

Room Temperature ◽

Quantum Cascade ◽

Well Design

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High photoresponse in room temperature quantum cascade detector based on coupled quantum well design

Applied Physics Letters ◽

10.1063/1.4973582 ◽

2016 ◽

Vol 109 (26) ◽

pp. 261107 ◽

Cited By ~ 11

Author(s):

Tatsuo Dougakiuchi ◽

Kazuue Fujita ◽

Toru Hirohata ◽

Akio Ito ◽

Masahiro Hitaka ◽

...

Keyword(s):

Quantum Well ◽

Room Temperature ◽

Quantum Cascade ◽

Well Design ◽

Coupled Quantum Well

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Leakages suppression by isolating the desired quantum levels for high-temperature terahertz quantum cascade lasers

Scientific Reports ◽

10.1038/s41598-021-02301-3 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Li Wang ◽

Tsung-Tse Lin ◽

Mingxi Chen ◽

Ke Wang ◽

Hideki Hirayama

Keyword(s):

High Temperature ◽

Quantum Well ◽

Room Temperature ◽

Quantum Cascade Lasers ◽

Quantum Cascade ◽

Thermally Activated ◽

High Fraction ◽

Consistent Method ◽

Cascade Lasers ◽

Non Equilibrium Green’S Function

AbstractThe key challenge for terahertz quantum cascade lasers (THz-QCLs) is to make it operating at room-temperature. The suppression of thermally activated leakages via high lying quantum levels is emphasized recently. In this study, we employ the advanced self-consistent method of non-equilibrium Green’s function, aiming to reveal those kinds of leakages in the commonly used THz-QCL designs based on 2-, 3- and 4-quantum well. At the high temperature of 300 K, if all the confined high lying quantum levels and also the continuums are included within three neighboring periods, leakages indeed possess high fraction of the total current (21%, 30%, 50% for 2-, 3- and 4-quantum well designs, respectively). Ministep concept is introduced to weaken those leakage channels by isolating the desired levels from high lying ones, thus the leakages are well suppressed, with corresponding fractions less than 5% for all three designs.

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Evidence of Intersubband Linewidth Narrowing Using Growth Interruption Technique

Photonics ◽

10.3390/photonics6020038 ◽

2019 ◽

Vol 6 (2) ◽

pp. 38 ◽

Cited By ~ 1

Author(s):

Ngoc Tran ◽

Giorgio Biasiol ◽

Arnaud Jollivet ◽

Alberto Bertocci ◽

François Julien ◽

...

Keyword(s):

Impurity Scattering ◽

Undoped Sample ◽

Interface Roughness ◽

Threshold Intensity ◽

Scattering Mechanism ◽

Intersubband Transitions ◽

Growth Interruption ◽

Ionized Impurity Scattering ◽

Interface Roughness Scattering ◽

Coherent Emission

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.

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Erratum: “High photoresponse in room temperature quantum cascade detector based on coupled quantum well design” [Appl. Phys. Lett. 109, 261107 (2016)]

Applied Physics Letters ◽

10.1063/1.4978208 ◽

2017 ◽

Vol 110 (10) ◽

pp. 109902

Author(s):

Tatsuo Dougakiuchi ◽

Kazuue Fujita ◽

Toru Hirohata ◽

Akio Ito ◽

Masahiro Hitaka ◽

...

Keyword(s):

Quantum Well ◽

Room Temperature ◽

Quantum Cascade ◽

Well Design ◽

Coupled Quantum Well

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FANSTEEL 85 METAL

Alloy Digest ◽

10.31399/asm.ad.cb0007 ◽

1981 ◽

Vol 30 (6) ◽

Keyword(s):

High Temperature ◽

Physical Properties ◽

Creep Strength ◽

Room Temperature ◽

Elevated Temperatures ◽

Base Alloy ◽

Heat Treating ◽

Good Combination ◽

Bend Strength ◽

Temperature Performance

Abstract FANSTEEL 85 METAL is a columbium-base alloy characterized by good fabricability at room temperature, good weldability and a good combination of creep strength and oxidation resistance at elevated temperatures. Its applications include missile and rocket components and many other high-temperature parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-7. Producer or source: Fansteel Metallurgical Corporation. Originally published December 1963, revised June 1981.

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MAGNESIUM AZ31B

Alloy Digest ◽

10.31399/asm.ad.mg0053 ◽

1962 ◽

Vol 11 (9) ◽

Keyword(s):

High Temperature ◽

Magnesium Alloy ◽

Physical Properties ◽

Room Temperature ◽

Heat Treating ◽

General Purpose ◽

Bearing Strength ◽

Temperature Performance ◽

Wrought Magnesium Alloy ◽

Metal Products

Abstract Magnesium AZ31B is a general purpose wrought magnesium alloy for room temperature service. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and compressive, shear, and bearing strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, and joining. Filing Code: Mg-53. Producer or source: The Dow Metal Products Company.

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Mass spectrometric study of allyl radical, allyl bromide and 1,5-hexadiene interactions with oxides; Cobalt suboxide Co3O4

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19792009 ◽

1979 ◽

Vol 44 (7) ◽

pp. 2009-2014 ◽

Cited By ~ 2

Author(s):

Jana Nováková ◽

Zdeněk Dolejšek

Keyword(s):

Room Temperature ◽

Allyl Bromide ◽

Catalytic Properties ◽

Mass Spectrometric Study ◽

Spectrometric Study ◽

Flow Conditions ◽

Allyl Radical ◽

Knudsen Flow ◽

Thermally Activated ◽

Radical Interaction

Products of (a) allyl radical interaction with unheated Co3O4, (b) thermally activated 1,5-hexadiene or thermally activated allyl bromide with unheated Co3O4, (c) moderately heated Co3O4 with unheated 1,5-hexadiene or allyl bromide were studied under Knudsen flow conditions. Cobalt suboxide Co3O4, a typical catalyst of deep oxidations yielded acrolein in reaction with allyl radicals as early as at the room temperature of the catalyst. A similar acrolein formation was also observed in the allyl radical interaction with other oxides exhibiting different catalytic properties. It appears that acrolein is in general the primary product of the allyl radical interaction with the oxides. The results are discussed and compared with previous data obtained with MoO3.

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