Phase-polarisation contrast for surface plasmon resonance biosensors

Area of Science:

• Optics and Photonics
• Biomedical Engineering
• Materials Science

Background:

• Surface Plasmon Resonance (SPR) is a label-free optical sensing technique widely used for detecting biomolecular interactions.
• Enhancing the contrast of SPR intensity profiles is crucial for improving sensor sensitivity and reducing detection limits.
• Current SPR techniques face limitations related to non-optimum coupling conditions and material parameter restrictions.

Purpose of the Study:

• To introduce and experimentally validate a new technique, phase-polarisation contrast (PPC), for enhancing SPR intensity profile contrast.
• To demonstrate the effectiveness of PPC under non-optimum SPR coupling conditions.
• To assess the impact of PPC on the performance and applicability of SPR sensors.

Main Methods:

• The proposed technique, phase-polarisation contrast (PPC), leverages the unique phase and polarisation properties of light during SPR.
• Experimental realization involved applying the PPC scheme to an SPR setup.
• The method was tested under conditions that are typically non-optimum for standard SPR coupling.

Main Results:

• PPC significantly enhances the contrast of the SPR intensity profile, exceeding one order of magnitude.
• The technique effectively lowers the resonant minimum of reflected intensity close to zero.
• This results in a substantial increase in the ratio of intensity at resonance to the minimum intensity.

Conclusions:

• The phase-polarisation contrast (PPC) technique offers a substantial improvement in SPR signal contrast.
• PPC reduces the stringent requirements for SPR-supporting metal films and biomolecular layers, simplifying sensor design and operation.
• The method facilitates SPR observation and increases the accuracy of SPR shift measurements, making it suitable for commercial SPR sensors.