Surface Plasmon Resonance-Based Fiber and Planar Waveguide Sensors

Figure 11

A dual LPG-based SPR sensor. The first LPG couples a guided mode to a particular cladding mode which has a small SPP component (the hybrid mode). The second step is the recoupling of the hybrid surface Plasmon wave back to the guided mode at the output of the fibre. A phase change is imparted by the introduction of the analyte, which detunes the coupling at the second LPG, resulting in an amplitude change at the output [27].