Polymer Waveguide Sensor Based on Localized Surface Plasmon Resonance for NaCl Solution Detection

In this paper, a polymer waveguide sensor based on localized surface plasmon resonance (LSPR) of gold nanoparticles was demonstrated. Gold nanoparticles with diameter of 20 nm were synthesized. Polymer SU-8 3050 material was used as core material to fabricate waveguides by standard photolithography. After silanization process, gold nanoparticles were efficiently and firmly bound to the polymer waveguide surface. Different concentrations of NaCl solution with the refractive index between 1.342 and 1.379 were detected by the polymer waveguide sensor coated with gold nanoparticles. A set of test system for polymer waveguide sensor was established and used to do the absorbance test in NaCl solution. The sensitivity is $\mathbf{4.016\Delta\ A/RIU}$ which is about 38 times higher than that of polymer film.