Where is the orbital angular momentum in vortex superposition states?

Area of Science:

• Optical physics
• Quantum optics
• Light-matter interactions

Background:

• Orbital angular momentum (OAM) is a fundamental property of light.
• Coaxial vortex superposition states involve combining multiple light beams with OAM.
• Understanding OAM distribution is crucial for applications in optical manipulation and communication.

Purpose of the Study:

• To explore the spatial distribution of OAM in coaxial vortex superposition states.
• To identify and characterize singular points within the intensity distribution of these states.
• To demonstrate the conservation of OAM during the coaxial interference process.

Main Methods:

• Applying the independent propagation principle of light for coaxial vortex superposition.
• Analyzing the spatial intensity distribution to locate singular points.
• Drawing analogies with rigid body angular momentum superposition for theoretical insights.

Main Results:

• Identified two types of singular points in the spatial intensity distribution.
• Proposed that the center singular point's topological charge is doubled by the number of superposition components.
• Showed that singular points at overlapping angular regions are shared by superposition components.
• Confirmed that the total OAM equals the sum of OAM in superposition states, demonstrating conservation.

Conclusions:

• The study elucidates the complex OAM distribution in coaxial vortex superposition states.
• Singular points play a key role in determining the topological charge and OAM.
• Orbital angular momentum is conserved throughout the coaxial interference process.