Broad detecting range of objective-based surface plasmon resonance sensor via multilayer structure

The demand of pursuing higher resolution drives the instrumental development of a surface plasmon resonance (SPR) sensor to shift from Kretchmann to objective-based configuration. However, its maximum sensing refractive index is restricted by the numerical aperture of an objective lens. Based on the mode conversion, we proposed a multilayer structure to extend the detecting range up to 11% (from 1.28 to 1.42) for a 1.45 objective lens via a transformed SPR mode. This technique not only overcomes intrinsic constraint but also reduces the cost.