Numerical simulation of phase-optimized light beams in two-dimensional scattering media

Area of Science:

• Biomedical optics
• Wave scattering phenomena
• Computational electromagnetics

Background:

• Manipulating incident wavefronts is crucial for deep light penetration and energy delivery in scattering biological tissues.
• Focusing light and characterizing electromagnetic fields within scattering media remain significant challenges.
• Electromagnetic field simulations are vital for understanding wavefront shaping and focal field evolution at depth.

Purpose of the Study:

• To simulate light scattering and focal intensity evolution within 2D scattering media using a novel two-step beam synthesis method.
• To investigate the impact of phase optimization on light focus intensity over depth.
• To analyze the enhancement factor of phase-optimized versus non-optimized beams under varying conditions.

Main Methods:

• Utilized a two-step beam synthesis approach combining plane wave electromagnetic near-field solutions and an angular spectrum method.
• Simulated scattering of complex incident wavefronts in well-characterized 2D scattering media.
• Investigated focus intensity over depth with and without phase optimization, analyzing enhancement factors.

Main Results:

• Non-optimized beams exhibited exponential decay in focus intensity at two distinct regions.
• Phase-optimized beams showed focus intensity progression over depth consistent with radiative transfer theory.
• Theoretically predicted enhancement factors were not fully realized due to channel correlations, especially with many optimization channels.

Conclusions:

• Phase optimization significantly improves focus intensity depth in scattering media.
• Channel correlations limit the achievable enhancement, reducing the gap between theoretical and simulated factors.
• Increased focus depth and numerical aperture decrease the discrepancy between theoretical and simulated enhancement factors.