Locally excited surface plasmon resonance for refractive index sensing with high sensitivity and high resolution

An angle-interrogated surface plasmon resonance (SPR) sensor based on a prism-coupled configuration has been extensively applied in biomedicine, environment monitoring, and food safety. Yet, the low sensitivity and low spatial resolution impede its further development. In this Letter, we investigated objective-coupled locally excited SPR for refractive index (RI) sensing with high sensitivity and high resolution. Through theoretical analysis, the SPR angle was retrieved from back focal plane imaging, which was highly correlated to the RI of the surrounding medium. Experimentally, a RI sensitivity of 77.41 degrees refractive index unit (RIU)(-1) was achieved with a detection range of 0.068 RIU when using glucose solutions for the demonstration. Furthermore, we acquired the spatial resolution of the configuration being 290 nm, and the RI measurement to a polydimethylsiloxane droplet with high spatial resolution was implemented. As a result, compared with the classical prism-coupled configuration, the locally excited SPR provides a method to achieve RI sensing with high sensitivity and high resolution. (C) 2021 Optical Society of America

Automated summary

The study introduces a method of objective-coupled locally excited SPR sensing with high sensitivity and high resolution for refractive index measurement. Through experimental and theoretical analysis, successful achievement of sensitivity and spatial resolution for the refractive index measurement of the medium was demonstrated.