Detecting Polarized Side-Scattering Signals in Media with Ultra-Low-Scattering Coefficients: An Improved Monte Carlo...

Polarized side-scattering techniques are widely used in aerosol detection, oceanographic optics, and biomedical sensing due to their high sensitivity to weak optical signals in low-scattering coefficient media. Conventional polarized Monte Carlo methods face significant challenges in such regimes due to geometric mismatch, where photon exit positions deviate substantially from the detector plane. This study addresses the geometric mismatch issue in polarized Monte Carlo simulations for side scattering in low-scattering media (scattering coefficient μs= 1 cm^-1), where photon exit positions often deviate from the detector plane. We propose a novel algorithm incorporating backward ray tracing with geometric projection correction to enhance simulation accuracy. Experimental validation was conducted using 532 nm laser illumination on both 500 nm polystyrene microspheres (μs= 0.21 cm^-1) and 5 nm TiO₂ nanoparticles (μs= 1.06 × 10^-6-1.06 × 10^-5 cm^-1). The results demonstrate excellent agreement between simulations and experiments, confirming the algorithm's capability to accurately capture the polarization characteristics of side-scattered light. This work provides a high-fidelity simulation tool for designing optical sensors in low-scattering media and holds direct applicability in nanoparticle concentration sensing and aerosol monitoring.