Multipulse dynamics of a passively mode-locked semiconductor laser with delayed optical feedback

Area of Science:

• Nonlinear Optics
• Semiconductor Lasers
• Dynamical Systems

Background:

• Passively mode-locked semiconductor lasers are vital for generating high-repetition-rate short pulses.
• Time-delayed optical feedback is a significant factor influencing laser dynamics and stability.
• Understanding these dynamics is crucial for controlling laser output and preventing undesirable behaviors.

Purpose of the Study:

• To investigate the complex dynamics and bifurcations in passively mode-locked semiconductor lasers with time-delayed optical feedback.
• To analyze the influence of pump current, feedback strength, and feedback delay time on laser behavior.
• To explore the role of resonances between mode-locking frequencies and feedback delay.

Main Methods:

• Modeling the laser system using delay differential equations incorporating cavity and feedback loop delays.
• Utilizing specialized path continuation software for analyzing short feedback delay regimes.
• Systematically varying pump current, feedback strength, and feedback delay time to observe bifurcations.

Main Results:

• Identified feedback-induced harmonic mode locking.
• Demonstrated that frequency mismatches can lead to multi-pulse or quasiperiodic dynamics.
• Observed slow modulation in quasiperiodic dynamics due to torus bifurcations and gain competition.

Conclusions:

• Resonances between mode-locking frequencies and feedback delay time play a critical role in laser dynamics.
• Time-delayed feedback can induce complex behaviors, including harmonic mode locking and multi-pulse operation.
• Increasing feedback delay leads to increased multistability between mode-locked solutions due to frequency pulling.