Determining the linewidth enhancement factor via optical feedback in quantum dot micropillar lasers

Area of Science:

• Semiconductor laser physics
• Quantum optics
• Photonics

Background:

• The linewidth enhancement factor (α) is crucial for understanding semiconductor laser dynamics and spectral properties.
• Accurate determination of α is essential for laser design and performance optimization.

Purpose of the Study:

• To develop and demonstrate a novel method for directly measuring the linewidth enhancement factor (α).
• To investigate the pump current dependence of α in high-β quantum dot micropillar lasers.

Main Methods:

• Direct measurement of laser gain and emission spectrum variations under delayed optical feedback.
• Comparison of the novel method with conventional techniques (linewidth comparison above/below threshold, injection locking).
• Quantitative description using simulations based on a quantum-optical model.

Main Results:

• Successfully demonstrated a new method for determining the linewidth enhancement factor (α).
• Quantified the pump current dependence of α for a high-β quantum dot micropillar laser.
• Validated the proposed method against established techniques, showing good agreement.

Conclusions:

• The proposed method offers a direct and accurate way to determine the linewidth enhancement factor (α) in semiconductor lasers.
• The study provides insights into the pump power dependence of α in quantum dot lasers.
• This technique can aid in the characterization and design of advanced semiconductor laser devices.