Surface-Plasmon-Resonance Refractive-Index Sensor With Cu-Coated Polymer Waveguide

We propose a refractive-index sensor based on the principle of surface plasmon resonance (SPR) in a polymer channel waveguide coated with a copper (Cu) film. Our fabricated device using a 40-nm Cu film covered with a 10-nm silicon-dioxide protecting layer offers a maximum refractive-index sensitivity of ~45 μm/RIU for the refractive-index range from 1.5375 to 1.5515, which is far more sensitive than the existing fiber/waveguide-based SPR sensors. The experimental results agree well with the theoretical analysis. We also present a sensor design with a record-high sensitivity of ~250 μm/RIU for aqueous solutions by using low-index polymer materials. The proposed sensor structure could be developed for a wide range of biomedical applications.