Spatial intensity correlations of a vortex beam and a perfect optical vortex beam

Area of Science:

• Optics and Photonics
• Wave Phenomena
• Scattering Theory

Background:

• Optical vortex beams and perfect optical vortex (POV) beams are crucial in various applications.
• Understanding the spatial coherence and speckle characteristics of these beams is essential for predicting their behavior upon scattering.
• Previous models may not fully capture the nuances of coherence evolution for these specific beam types.

Purpose of the Study:

• To develop a model for the spatial coherence function of random fields generated by scattering optical vortex and perfect optical vortex beams.
• To analytically, numerically, and experimentally investigate the dependence and independence of speckle size on the topological charge for optical vortex and POV beams, respectively.
• To explore the propagation distance effects on speckle size and spatial coherence for both beam types.

Main Methods:

• Utilizing a model based on the Fresnel diffraction scheme.
• Calculating the spatial coherence function for scattered optical vortex and POV beams.
• Performing analytical, numerical, and experimental analyses.
• Investigating the speckle size dependence on topological charge and propagation distance.

Main Results:

• Demonstrated the dependence of speckle size on topological charge for optical vortex beams.
• Showed the independence of speckle size on topological charge for perfect optical vortex (POV) beams.
• Confirmed a linear dependence of speckle size on the propagation distance for both beam types.
• Identified a regime where the spatial coherence function remains non-evolving with propagation distance for both beam types.

Conclusions:

• The spatial coherence function model accurately describes speckle characteristics of scattered optical vortex and POV beams.
• Speckle size behavior differs significantly between optical vortex and POV beams concerning topological charge.
• Speckle size scales linearly with propagation distance, a key factor in beam propagation analysis.
• The identification of a non-evolving spatial coherence function regime offers new insights into beam stability and applications.