Abstract

The performance of surface plasmon resonance (SPR) sensors can be different depending on which characteristic of the SPR sensor the amplitude or the phase is monitored. The phase sensitivity strongly depends on the geometry and the optical properties of the system. The existence of sharp changes in the phase spectrum variations is found as the thickness of SPR-supporting gold (dg) varies around a critical thickness (dc). In addition, the simulation results indicate that the phase sensitivity is divided into two regions so that phase sensitivity Sj for region dg  dc is greater than region dg>dc. It is demonstrated in condition of dg < dc the phase sensitivity has a strong jump when the sensing medium refractive index lies within a certain interval, while the amplitude sensitivity has a monotonic shape. The phase analysis from another aspect exhibits that the phase maximum differenceΔjmax towards the blank sample is sensitive to refractive index in a continuous interval. As a result, the phase detection interval is tunable by varying the gold thickness, which potentially is important for medical, biology and chemistry applications.