Polarization interference interrogation of angular surface plasmon resonance sensors with wide metal film thickness tolerance

We apply the polarization interferometry (PI) technique to a one-dimensional SPR sensor based on angle interrogation, for improving the refractive index (RI) resolution and reducing the dependence of RI resolution on the thickness of metal films. We demonstrate experimentally that the PI technique could reduce the minimum of the SPR angular spectrum, and improve the RI resolution of the sensors with non-optimal metal films, reducing the dependence of the RI resolution on the thickness of metal films. Furthermore, the application of PI technique at the angles, which are smaller than the original angle affording the minimum, could further improve the RI resolution of the system even better than the original optimal condition. RI resolution ranging from 1.2 to 2.2 × 10−7 refractive index unit (RIU) is achieved with the thickness of the Au film ranging from 28.2 to 54.4 nm. The PI technique has potential applications in producing SPR sensors with high RI resolution and wide metal film thickness tolerance.