An indirectly pumped terahertz quantum cascade laser with low injection coupling strength operating above 150 K
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 GaA...
| Principais autores: | , , , , , , , , , , , |
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| Outros Autores: | |
| Formato: | Artigo |
| Idioma: | en_US |
| Publicado em: |
American Institute of Physics (AIP)
2014
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| Acesso em linha: | http://hdl.handle.net/1721.1/87016 https://orcid.org/0000-0003-1982-4053 |
| Resumo: | 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. |
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