Phase instability in semiconductor lasers.

Area of Science:

• Nonlinear dynamics
• Laser physics
• Fluid dynamics

Background:

• Lasers have long been considered peculiar nonlinear oscillators due to the apparent absence of phase instability in standard models.
• This perceived stability has limited the understanding of complex laser dynamics.

Purpose of the Study:

• To re-evaluate the fundamental equations governing laser dynamics.
• To investigate the potential for phase instability in lasers.
• To explain the deterministic multimode dynamics observed in experimental results.

Main Methods:

• A rigorous derivation of fundamental laser equations using codimension 2 bifurcation theory.
• Analysis of potential dynamical regimes, including pure phase instability and mixed phase-amplitude turbulence.
• Comparison of theoretical predictions with existing experimental data.

Main Results:

• The apparent absence of phase instability in lasers is an artifact of approximations in standard models.
• New theoretical framework reveals dynamical regimes with pure phase instability or mixed phase-amplitude turbulence.
• The Benjamin-Feir instability, a known phenomenon in nonlinear waves, provides a satisfactory explanation for deterministic multimode laser dynamics.

Conclusions:

• The Benjamin-Feir instability is a fundamental mechanism driving multimode dynamics in lasers.
• Revisiting laser models with advanced bifurcation theory uncovers previously unrecognized instabilities.
• This work reconciles theoretical predictions with experimental observations in nonlinear laser systems.