Mid-IR quantum dot cascade VCSEL: feasibility study and feature extraction

Area of Science:

• Optoelectronics
• Semiconductor Lasers
• Nanotechnology

Background:

• Quantum cascade lasers (QCLs) offer efficient light emission but face limitations.
• Quantum wells in QCLs can be improved by using quantum dots (QDs).
• Vertical cavity surface emitting lasers (VCSELs) are known for energy efficiency.

Purpose of the Study:

• Introduce a novel quantum dot cascade VCSEL (QDC-VCSEL) concept.
• Design and predict features of a QDC-VCSEL operating at 4.5 µm.
• Investigate the performance and design dependencies of QDC-VCSELs.

Main Methods:

• Optimized cavity and active region for TE mode using high contrast gratings.
• Developed rate equations for the cascade scheme to analyze laser characteristics.
• Studied the impact of design parameters, particularly carrier tunneling time, on performance.

Main Results:

• Predicted QDC-VCSEL performance at 4.5 µm wavelength.
• Achieved output peak powers of ~2 mW at 150 K and ~0.5 mW at 273 K.
• Demonstrated that increased tunneling time reduces modulation bandwidth and increases threshold current.

Conclusions:

• The QDC-VCSEL concept successfully combines QD laser advantages with VCSEL efficiency.
• Design optimization is crucial for achieving desired performance metrics.
• Carrier tunneling time is a key parameter influencing QDC-VCSEL characteristics.