Coherent coupling of multiple transverse modes in quantum cascade lasers

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Nonlinear Dynamics

Background:

• Quantum cascade lasers (QCLs) possess unique properties like high intracavity intensity and strong optical nonlinearity.
• Their complex relaxation time scales make them ideal for studying nonlinear laser dynamics.

Purpose of the Study:

• To investigate the nonlinear coupling between transverse modes in QCLs.
• To provide evidence for stable phase coherence among multiple transverse modes.

Main Methods:

• Experimental measurements of spectral data.
• Near-field and far-field mode profile analysis.
• Theoretical modeling of four-wave mixing interactions.

Main Results:

• Stable phase coherence of multiple transverse modes was observed across a wide range of injection currents.
• Evidence supports a four-wave mixing interaction as the mechanism for phase coherence.
• Experimental data aligns with theoretical predictions for phase-locking conditions.

Conclusions:

• Nonlinear coupling leads to stable phase coherence in QCL transverse modes.
• Four-wave mixing is identified as the key interaction responsible for this phase-locking.
• The findings enhance understanding of nonlinear dynamics in QCLs.