An indirectly pumped terahertz quantum cascade laser with low injection coupling strength operating above 150 K
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Author(s)
Razavipour, S. G.
Dupont, E.
Fathololoumi, S.
Lindskog, M.
Wasilewski, Z. R.
Aers, G.
Laframboise, Sylvain R.
Wacker, A.
Ban, D.
Liu, H. C.
Date Issued
May 2013
Journal
Journal of Applied Physics
Publisher
American Institute of Physics (AIP)
Citation
Razavipour, S. G., E. Dupont, S. Fathololoumi, C. W. I. Chan, M. Lindskog, Z. R. Wasilewski, G. Aers, et al. “An Indirectly Pumped Terahertz Quantum Cascade Laser with Low Injection Coupling Strength Operating Above 150 K.” Journal of Applied Physics 113, no. 20 (2013): 203107. © 2013 AIP Publishing LLC
Version
Final published version
Abstract
We 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/Al[subscript 0.25]Ga[subscript 0.75]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[superscript +] GaAs contact layer lased at 2.4 THz up to 128.5 K, while another one without the top n[superscript +] GaAs lased up to 152.5 K ( 1.3ℏω/k[subscript B] ). 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.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1063/1.4807580
