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Gain competition in dual wavelength quantum cascade lasers
Markus Geiser1, Christian Pflügl, Alexey Belyanin
1School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, USA.
Optics Express
|July 1, 2010
Summary
Dual wavelength quantum cascade lasers show mode competition, where lower threshold modes deplete gain for higher threshold modes. A rate equation model quantifies this mutual gain depletion effect.
Area of Science:
- Optics and Photonics
- Semiconductor Lasers
- Quantum Cascade Lasers
Background:
- Heterogeneous cascades enable dual wavelength emission in quantum cascade lasers.
- Mode competition is a critical factor affecting laser performance and stability.
Purpose of the Study:
- Investigate dual wavelength operation in mid-infrared quantum cascade lasers.
- Analyze the impact of gain competition on laser modes.
- Develop a model to describe inter-mode interactions.
Main Methods:
- Fabrication and characterization of heterogeneous cascade lasers.
- Experimental observation of dual wavelength laser action.
- Development of a rate equation model for mode coupling analysis.
Main Results:
- Laser action initiated in higher-order lateral modes due to gain competition.
- Lower threshold mid-infrared mode reduced population inversion for the second laser via stimulated emission.
- Quantitative description of mutual gain depletion achieved by the rate equation model.
Conclusions:
- Gain competition significantly influences mode selection in dual wavelength quantum cascade lasers.
- Stimulated emission from lower threshold modes acts as a loss mechanism for higher threshold modes.
- The developed rate equation model accurately captures the complex mode interactions in these devices.
