Measurement-Aware Computational Modeling for Optical Spectrometry in Scattering-Dominated Systems

Area of Science:

• Computational modeling
• Optical spectrometry
• Photon transport physics

Background:

• Current computational models often extrapolate isolated-particle optical properties to finite concentrations, neglecting crucial factors like multiple scattering and instrument geometry.
• This simplification leads to systematic discrepancies in scattering-dominated systems, misinterpreting experimental extinction and polarization data.

Purpose of the Study:

• To develop a measurement-aware, physics-guided computational framework that integrates electrodynamic theory with Monte Carlo photon transport simulations.
• To accurately model photon trajectories within finite sample volumes, explicitly including multiple scattering and detector collection constraints for realistic experimental conditions.
• To enable quantitative comparison between theoretical predictions and experimental measurements by inferring effective parameters like collection geometry and refractive index.

Main Methods:

• Integration of electrodynamic theory with Monte Carlo photon transport simulations.
• Supervised least-squares parameter estimation under realistic experimental conditions.
• Cross-validated regression for inferring effective parameters (collection geometry, refractive index) from experimental data.

Main Results:

• The framework accurately reproduces UV-Vis extinction spectra of polystyrene suspensions across various sizes and concentrations, capturing nonlinear concentration dependence.
• It explains deviations from Beer-Lambert law predictions in concentrated systems due to geometry-dependent photon redistribution, showing measured optical densities below predicted values.
• Simulations demonstrate that multiple scattering significantly alters intensity and polarization in a concentration- and aperture-dependent manner.

Conclusions:

• The developed framework provides a quantitative method for reconciling theoretical predictions with experimental measurements in scattering-dominated optical systems.
• It enables consistent extraction of effective refractive indices across different particle sizes and datasets by explicitly accounting for transport effects.
• This approach offers a scalable pathway for modeling more complex absorbing and emissive materials in optical spectrometry.