A Simple Phase-Sensitive Surface Plasmon Resonance Sensor Based on Simultaneous Polarization Measurement Strategy

• Published in: Sensors (Basel, Switzerland) Vol. 21; no. 22; p. 7615
• Main Authors: Li, Meng-Chi, Chen, Kai-Ren, Kuo, Chien-Cheng, Lin, Yu-Xen, Su, Li-Chen
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 16.11.2021; MDPI
• Subjects: Algorithms; Chromatography; Communication; Interferometry; Light; Optics; phase-sensitive SPR; phase-shift interferometry; pixelated micropolarizer array; Questioning; Sensors
• DOI: 10.3390/s21227615
• ISSN: 1424-8220

The SPR phenomenon results in an abrupt change in the optical phase such that one can measure the phase shift of the reflected light as a sensing parameter. Moreover, many studies have demonstrated that the phase changes more acutely than the intensity, leading to a higher sensitivity to the refractive index change. However, currently, the optical phase cannot be measured directly because of its high frequency; therefore, investigators usually have to use complicated techniques for the extraction of phase information. In this study, we propose a simple and effective strategy for measuring the SPR phase shift based on phase-shift interferometry. In this system, the polarization-dependent interference signals are recorded simultaneously by a pixelated polarization camera in a single snapshot. Subsequently, the phase information can be effortlessly acquired by a phase extraction algorithm. Experimentally, the proposed phase-sensitive SPR sensor was successfully applied for the detection of small molecules of glyphosate, which is the most frequently used herbicide worldwide. Additionally, the sensor exhibited a detection limit of 15 ng/mL (0.015 ppm). Regarding its simplicity and effectiveness, we believe that our phase-sensitive SPR system presents a prospective method for acquiring phase signals.