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Mode-locked pulses from mid-infrared quantum cascade lasers
Christine Y Wang1, Lyuba Kuznetsova, V M Gkortsas
1Department of Physics and 2School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138, USA.
Optics Express
|August 6, 2009
Summary
This study demonstrates mid-infrared mode-locked pulses from quantum cascade lasers (QCLs) using gain modulation. The generated 3 ps pulses were characterized and modeled, revealing insights into mode-locking dynamics.
Area of Science:
- Quantum optics
- Semiconductor lasers
Background:
- Quantum cascade lasers (QCLs) are semiconductor devices capable of emitting light in the mid-infrared spectrum.
- Mode-locking is a technique used to generate ultrashort pulses of light.
Purpose of the Study:
- To unequivocally demonstrate mid-infrared mode-locked pulses from quantum cascade lasers.
- To model the mode-locking dynamics in QCLs.
Main Methods:
- Actively modulating the gain of an edge-emitting quantum cascade laser (QCL).
- Characterizing the generated pulses using second-order interferometric autocorrelation with a nonlinear quantum well infrared photodetector.
- Modeling mode-locking dynamics using Maxwell-Bloch equations in an open two-level system.
Main Results:
- Successful generation of short pulses with a duration of approximately 3 ps and energy of 0.5 pJ.
- The developed model accurately reproduces measured autocorrelation traces.
- The model predicts substantial pulse wings due to spatial hole burning.
Conclusions:
- Mid-infrared mode-locked pulses can be reliably generated from quantum cascade lasers.
- The Maxwell-Bloch model provides valuable insights into the underlying physics of QCL mode-locking.
- Understanding spatial hole burning is crucial for optimizing pulse characteristics.
