Narrow linewidth optical frequency comb based on a directly modulated microcavity laser with optical feedback.

Area of Science:

• Photonics and Optical Engineering
• Laser Physics
• Semiconductor Devices

Background:

• Microcavity lasers offer high electro-optical response.
• Optical frequency combs (OFCs) are crucial for precise frequency metrology.
• Achieving narrow linewidth OFCs is essential for advanced applications.

Purpose of the Study:

• To numerically investigate and experimentally demonstrate a narrow linewidth OFC.
• To optimize OFC generation using external optical feedback in a microcavity laser.
• To analyze the impact of feedback strength and phase on OFC properties.

Main Methods:

• Numerical simulations using rate equations to model laser dynamics.
• Experimental implementation of a directly modulated microcavity laser with external optical feedback.
• Utilizing a dual-loop feedback structure to suppress side modes.

Main Results:

• Optimized feedback conditions significantly improved linewidth properties.
• Demonstrated robustness of the OFC against variations in feedback strength and phase.
• Achieved a 15-tone OFC with a 10 GHz frequency interval and 31 dB side-mode suppression ratio.
• Measured a comb tooth linewidth of approximately 7 kHz, a 2000-fold compression.

Conclusions:

• Directly modulated microcavity lasers with external feedback are effective for generating narrow linewidth OFCs.
• The dual-loop feedback structure enhances OFC quality by suppressing side modes.
• This method offers a promising approach for high-performance OFC generation.