Counterpropagating optical vortices in photorefractive crystals

Area of Science:

• Nonlinear optics
• Photorefractive materials
• Vortex beam dynamics

Background:

• Incoherent vortices in nonlinear media exhibit complex dynamics.
• Understanding beam stability and momentum conservation is crucial for applications.

Purpose of the Study:

• To comprehensively study (2+1)D counterpropagating incoherent vortices in photorefractive crystals.
• To investigate the role of angular momentum conservation in stable and unstable beam propagation.
• To discover novel vortex beam structures and dynamics.

Main Methods:

• Numerical simulations of a (2+1)D local isotropic dynamical model.
• Analysis of Kerr-type saturable nonlinearity.
• Analytical and numerical verification of conserved quantities, including angular momentum.

Main Results:

• Stable counterpropagating vortex beams conserve angular momentum.
• Angular momentum becomes non-conserved upon loss of stability due to radiation or inelastic collisions.
• Novel rotating beam structures, unique to counterpropagation, were discovered.
• Transition from few-beam propagation to transverse pattern formation dynamics was observed for complex beam arrangements.

Conclusions:

• Angular momentum conservation is a key indicator of stability for counterpropagating incoherent vortices.
• The study reveals new possibilities for generating and controlling complex light structures in nonlinear media.