Surface plasmon resonance (SPR) has found wide applications in sensing down to molecular level due to its extreme sensitivity to change of dielectric properties. An unavoidable effect in SPR is surface deformation (thermal bump) due to local heating by incident laser light used in SPR excitation. In addition, the change in reflection phase from an SPR-supported metal film could also contribute to the SPR signal variation, and thus proper handling of measured SPR signals is very important in order to broaden its potential applications. Here a simple Fabry Perot (FP) interference technique for measuring, simultaneously, the thermal bump as well as the reflection phase shift of the gold film used for SPR excitation is reported. The FP signal change is dominated by the appearance of...[ Read more ]

Surface plasmon resonance (SPR) has found wide applications in sensing down to molecular level due to its extreme sensitivity to change of dielectric properties. An unavoidable effect in SPR is surface deformation (thermal bump) due to local heating by incident laser light used in SPR excitation. In addition, the change in reflection phase from an SPR-supported metal film could also contribute to the SPR signal variation, and thus proper handling of measured SPR signals is very important in order to broaden its potential applications. Here a simple Fabry Perot (FP) interference technique for measuring, simultaneously, the thermal bump as well as the reflection phase shift of the gold film used for SPR excitation is reported. The FP signal change is dominated by the appearance of the thermal bump while it is small for the effect of the reflection phase shift due to the change of dielectric property of the metal. To support the experimental results, model simulations for the SPR system are performed and good agreement with the experiment is obtained. The effect of the thermal bump on the resonance of surface plasmon is also investigated and a polarization-dependent reflection phase shift is observed in SPR. Since both amplitude and phase can be measured, our method could lead to a better characterization of SPR and can also be applied to the study of active metasurfaces under external excitation.