Spectral Behavior of Linewidth Enhancement Factor of a Mid-Infrared Quantum Cascade Laser
| Autor: | Naoki Kumazaki, Tadataka Edamura, Kenichi Kasahara, Atsushi Sugiyama, Yohei Takagi, Naota Akikusa, Mikito Ishihara |
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| Rok vydání: | 2008 |
| Předmět: |
Physics
Physics and Astronomy (miscellaneous) business.industry media_common.quotation_subject General Engineering Physics::Optics General Physics and Astronomy Condensed Matter::Mesoscopic Systems and Quantum Hall Effect Laser Asymmetry law.invention Laser linewidth Optics Cascade law Atomic physics business Quantum cascade laser Lasing threshold Quantum media_common Diode |
| Zdroj: | Japanese Journal of Applied Physics. 47:6320-6326 |
| ISSN: | 1347-4065 0021-4922 |
| DOI: | 10.1143/jjap.47.6320 |
| Popis: | We report the experimental linewidth enhancement factor (α-factor) results on mid-infrared InGaAs/InAlAs quantum cascade lasers (QCLs) obtained using the self-mixing method. The waveforms appearing under self-mixing conditions were different from those originally predicted, which assumed that the gain was symmetric around the gain peak and that α=0. The signs of the QCL α-factors were identified to be negative and asymmetric to the gain peak by using the nonsymmetrical mirror drive, and by comparing their wave patterns to those of conventional 1.55-µm laser diodes. The nonparabolicity of the subbands was a possible cause of the α-factor's asymmetry. The subbands are no longer parallel if the lasing energy is restricted by the nonparabolicity, which produces inhomogeneous broadening and an asymmetric optical gain spectrum with a long wavelength tail. Taking the nonparabolicity into account, we determined the QCL gain spectrum and the dependence of the α-factor on the spectral position relative to the gain peak. The dependence of the α-factor on detuning was in reasonable agreement with the calculation that accounts for the asymmetry in gain. |
| Databáze: | OpenAIRE |
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