Dynamic measurement of an angular Goos–Hänchen shift at a surface plasmon resonance in liquid

Abstract

We developed a surface plasmon resonance (SPR)-enhanced angular Goos–Hänchen (GH) shift measurement system capable of tracking small refractive index changes with high sensitivity in a liquid environment. Our method can be performed in angular interrogation schemes, where we demonstrate a simple zero-finding algorithm to locate the SPR angle instead of the complicated data processing algorithms used in conventional sensors. We also propose a displacement interrogation scheme for dynamic measurement of small refractive index changes in the sample. The main advantage of our method is the controllability of the measured displacement by standard geometrical optics, allowing measurement sensitivity enhancement without the need to modify the sensor material.