Phase-sensitive time-modulated surface plasmon resonance polarimetry for wide dynamic range biosensing

Area of Science:

• Optics
• Biotechnology
• Materials Science

Background:

• Surface Plasmon Resonance (SPR) biosensors are crucial for label-free detection.
• Phase-sensitive SPR offers high sensitivity but often suffers from limited dynamic range.
• Improving the performance of SPR biosensors is essential for advanced diagnostics.

Purpose of the Study:

• To propose and validate a novel polarimetry scheme for enhancing phase-sensitive SPR biosensors.
• To improve the detection limit and maintain a wide dynamic range in SPR measurements.
• To demonstrate the biosensing capabilities of the proposed scheme using a model biological reaction.

Main Methods:

• Utilizing s-polarized light as a reference beam, unaffected by SPR.
• Analyzing the phase-polarization state of mixed polarization light for phase information.
• Employing temporal modulation of the reflected SPR beam with a photo-elastic modulator.
• Detecting signals at the 2nd and 3rd harmonics of the modulated frequency.

Main Results:

• The proposed scheme provides ultra-sensitive phase-based response to refractive index changes.
• Achieved significant improvement in detection limit compared to intensity-sensitive SPR.
• Maintained a wide dynamic range, overcoming a common limitation of phase-sensitive SPR.
• Successfully illustrated biosensing applications with an avidin-biotin binding model on gold.

Conclusions:

• The novel polarimetry scheme offers a significant advancement for phase-sensitive SPR biosensors.
• This method enhances sensitivity and dynamic range, making it suitable for various biosensing applications.
• The proposed technique holds promise for improved performance in label-free biomolecular detection.