Stabilizing DFB laser injection-locked to an external fiber-optic ring resonator

Area of Science:

• Optics and Photonics
• Semiconductor Laser Technology
• Laser Spectroscopy

Background:

• Self-injection locking enhances semiconductor laser performance by narrowing linewidth.
• Existing methods are sensitive to environmental and parameter fluctuations.
• Stable, single-mode operation is crucial for many laser applications.

Purpose of the Study:

• To develop a stable, mode-hop-free semiconductor laser.
• To investigate the use of active optoelectronic feedback with self-injection locking.
• To characterize the impact of this combined technique on laser linewidth and phase noise.

Main Methods:

• Implemented a novel laser configuration combining self-injection locking with active optoelectronic feedback.
• Utilized a 4-m length fiber resonator for external cavity locking.
• Analyzed laser dynamics with and without active feedback.

Main Results:

• Achieved stable, mode-hop-free, single longitudinal mode operation.
• Drastically narrowed the distributed feedback (DFB) laser linewidth to 2.8 kHz.
• Reduced laser phase noise by three orders of magnitude.
• Demonstrated stability and tunability of the laser linewidth.

Conclusions:

• Active optoelectronic feedback effectively overcomes the sensitivity limitations of self-injection locking.
• The proposed technique offers a robust method for achieving ultra-narrow linewidth and low phase noise semiconductor lasers.
• This approach provides enhanced stability and tunability for DFB lasers.