Ultra-narrow linewidth quantum dot coherent comb lasers with self-injection feedback locking.

Area of Science:

• Quantum optics
• Semiconductor lasers
• Photonics

Background:

• Quantum dot (QD) lasers offer unique properties for optical applications.
• Coherent comb lasers (CCL) are crucial for multi-wavelength applications.
• Optical linewidth and phase noise are critical performance metrics for lasers.

Purpose of the Study:

• To investigate the effectiveness of external cavity self-injection feedback locking (SIFL) for linewidth reduction in QD CCLs.
• To quantify the impact of SIFL on phase noise and RF signal quality.

Main Methods:

• Implementation of an external cavity self-injection feedback locking (SIFL) system.
• Simultaneous linewidth reduction of over 39 wavelength channels in an InAs/InP QD CCL.
• Measurement of optical linewidth, phase noise spectra, and RF beating signals.

Main Results:

• Optical linewidth reduced from MHz to sub-200 kHz for individual channels.
• Significant decrease in phase noise observed above 2 kHz.
• 3-dB linewidth of RF beating signals reduced from 10 kHz to 300 Hz, with baseline level dropping from -27 dB to -50 dB.

Conclusions:

• SIFL is a highly effective technique for simultaneously reducing the optical linewidth of multiple channels in QD CCLs.
• The SIFL system substantially improves laser phase noise and RF signal quality.
• This work demonstrates a significant advancement in QD laser performance for optical communication and sensing.