Mechanical modulation method for ultrasensitive phase measurements in photonics biosensing

Area of Science:

• Optical Physics
• Biomedical Sensing
• Metrology

Background:

• Phase-sensitive measurements are crucial for high-resolution optical biosensing.
• Existing methods often require complex setups or lack sufficient sensitivity.
• Optical transduction offers label-free detection capabilities for biological analytes.

Purpose of the Study:

• To introduce a novel polarimetry methodology for phase-sensitive measurements in a single reflection geometry.
• To demonstrate its application in optical transduction-based biological sensing.
• To evaluate its performance in Total Internal Reflection (TIR) and Surface Plasmon Resonance (SPR) configurations.

Main Methods:

• Utilized chopper-based mechanical phase modulation for orthogonal s- and p-polarized light.
• Extracted phase information at different harmonics of the modulation frequency.
• Investigated the methodology using both TIR and SPR geometries with varying prism materials.

Main Results:

• Achieved phase measurement resolution as low as 0.007 degrees with a simple experimental setup.
• Demonstrated a detection limit of 10⁻⁵ Refractive Index Unit (RIU) change for Si-based TIR.
• Showcased a detection limit of 3.2*10⁻⁷ RIU for SPR, indicating superior phase response.

Conclusions:

• The proposed polarimetry methodology offers high sensitivity and simplicity for optical biosensing.
• It provides excellent noise immunity due to stable modulation.
• The method is particularly effective in SPR configurations, achieving state-of-the-art sensitivity for phase-sensitive detection.