An indirectly pumped terahertz quantum cascade laser with low injection coupling strength operating above 150 K

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DOIResolve DOI: http://doi.org/10.1063/1.4807580
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TypeArticle
Journal titleJournal of Applied Physics
ISSN0021-8979
Volume113
Issue20
Article number203107
SubjectCoupling strengths; Fabricated device; Injection currents; Metal-metal waveguides; Non-equilibrium Green's function; Oscillator strengths; Population inversions; Terahertz quantum-cascade lasers; Gallium arsenide; Gold; Semiconducting gallium; Quantum cascade lasers
AbstractWe designed and demonstrated a terahertz quantum cascade laser based on indirect pump injection to the upper lasing state and phonon scattering extraction from the lower lasing state. By employing a rate equation formalism and a genetic algorithm, an optimized active region design with four-well GaAs / Al0.25 Ga0.75 As cascade module was obtained and epitaxially grown. A figure of merit which is defined as the ratio of modal gain versus injection current was maximized at 150 K. A fabricated device with a Au metal-metal waveguide and a top n+ GaAs contact layer lased at 2.4 THz up to 128.5 K, while another one without the top n+ GaAs lased up to 152.5 K (1.3ω/kB). The experimental results have been analyzed with rate equation and nonequilibrium Green's function models. A high population inversion is achieved at high temperature using a small oscillator strength of 0.28, while its combination with the low injection coupling strength of 0.85 meV results in a low current. The carefully engineered wavefunctions enhance the quantum efficiency of the device and therefore improve the output optical power even with an unusually low injection coupling strength.
Publication date
LanguageEnglish
AffiliationInformation and Communication Technologies; Security and Disruptive Technologies; National Research Council Canada
Peer reviewedYes
NPARC number21270464
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Record identifier8241dee6-ff57-401f-9626-fe7fcbd7ffc7
Record created2014-02-12
Record modified2016-05-09
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