Polarization-preservation analysis for robust reflection-mode optical glucose sensing in turbid media

Area of Science:

• Optics
• Biomedical Engineering
• Sensing Technology

Background:

• Non-invasive optical glucose sensing faces challenges in scattering media due to depolarization and absorption.
• Reflection-mode geometries complicate polarization signals, limiting conventional metrics.
• Multiple scattering conditions cause polarization scrambling, hindering accurate measurements.

Purpose of the Study:

• To investigate polarization-resolved reflection measurements for non-invasive glucose sensing.
• To introduce and evaluate a polarization-preservation ratio (PPR) for quantifying polarization preservation.
• To compare linear and circular polarization states for glucose detection in scattering phantoms.

Main Methods:

• Utilized skin-equivalent milk-based phantoms with varying glucose concentrations (50-400 mg dL⁻¹).
• Employed visible illumination at 532 and 660 nm with polarization-resolved reflection measurements.
• Introduced and assessed a polarization-preservation ratio (PPR) derived from circular polarization components, alongside the degree-of-polarization (DOP).

Main Results:

• Circular polarization combined with PPR showed stronger glucose-dependent correlations and improved stability compared to linear polarization.
• The proposed PPR metric demonstrated enhanced robustness in turbid environments, even with pigment interference at 660 nm.
• High correlation coefficients were maintained at 660 nm, indicating improved sensing capabilities.

Conclusions:

• Polarization-preservation analysis offers a physically consistent and robust sensing strategy for reflection-mode optical glucose detection.
• The novel PPR metric effectively quantifies polarization preservation in scattering media.
• This approach shows promise for overcoming limitations in non-invasive glucose monitoring.