Simultaneous Measurement of Optical Amplitude and Phase Spectra Using Beam-Scanning Angular Surface Plasmon Resonance Sensor with Heterodyne Interferometry

Refractive index (RI) sensing plays a crucial role in industrial applications and biosensing due to its ability to detect subtle changes in a medium's optical properties. Among various optical RI sensing techniques, surface plasmon resonance (SPR) [1] has emerged as a widely adopted method owing to its high sensitivity and specificity. In particular, the beam-scanning angular SPR sensor has been extensively utilized for its real-time measurement capability and moderate precision [2], [3]. However, there is a growing demand for further enhancement in its performance to meet the requirements of advanced applications. In this study, we introduce a heterodyne interferometer into the beam-scanning angular SPR sensor to achieve simultaneous acquisition of angular spectra of reflectance and phase. This integration allows for the retrieval of complex angular SPR spectra, providing enhanced sensing capabilities and a pathway toward higher precision and functionality in RI sensing.