SPR based biosensor using surface relief grating in transmission mode

Surface plasmon resonance platforms based on laser inscribed azo polymer surface relief diffraction gratings were used to detect the binding of organic and biological molecules. Optical sensors were assembled to operate in transmission mode, resulting in a very simple setup. This new approach is observed to present a high sensitivity when compared to other systems, such as SPR-based biosensors using nanoholes. The corrugated surface provides a relatively large surface area and the improved sensitivity to binding events is related to resonant plasmon enhancement on the surface relief grating. It was found that varying the periodicity from 400 to 410 nm does not improve efficiency, however changing the groove depth from 30 to 65 nm, resulted in a two-fold increase in sensitivity. An interesting result is that sensors with higher energy surface plasmons present higher sensitivity when compared to lower energy ones. This result can drive further studies toward improved surface plasmon-based sensors.