Impact of FBG feedback phase on laser dynamics

Area of Science:

• Optics and Photonics
• Semiconductor Laser Dynamics

Background:

• Fiber Bragg gratings (FBGs) are utilized to control chaotic properties in semiconductor lasers.
• Environmental sensitivity of FBGs is recognized, but feedback phase fluctuations are often overlooked.

Purpose of the Study:

• To experimentally investigate the impact of minor propagation time variations in FBGs on semiconductor laser behavior.
• To analyze the role of phase variations and offsets in laser stability.
• To validate experimental findings with theoretical simulations.

Main Methods:

• Experimental setup involving thermal tuning of a Fiber Bragg Grating coupled to a semiconductor laser.
• Observation and analysis of laser output characteristics under varying FBG thermal conditions.
• Numerical simulations using an expanded Lang-Kobayashi model.

Main Results:

• Small thermal variations in the FBG induce significant changes in semiconductor laser dynamics.
• Periodic enhancements in laser stability are observed and correlated with phase variations.
• Both phase variation and phase offset are identified as critical factors influencing laser behavior.

Conclusions:

• Thermal tuning of FBGs, even with small propagation time changes, significantly alters semiconductor laser characteristics.
• Feedback phase dynamics are crucial for understanding and controlling laser stability.
• The expanded Lang-Kobayashi model provides a good qualitative agreement with experimental observations.