Demonstration of Polarization-Independent Surface Plasmon Resonance Polymer Waveguide for Refractive Index Sensing

The effect of the variation of the refractive index in a gold-coated ormocomp waveguide for sensing application is studied in this paper. The ormocomp waveguide is fabricated by using the nanoimprint method. A waveguide with width and height both equal to 10 μm is coated with 100 nm thick gold using the sputtering technique in order to introduce surface plasmon resonance at the vertical sides and also at the top of the structure. Here, polarization-independent waveguide is achieved by supporting both the plasmonic TE and TM modes and the light confinement in these modes are studied. Supermodes forming from coupling between the fundamental dielectric mode and the plasmonic supermode at the resonance peak are also investigated. This paper presents the numerical simulated results and also their experimental validations. For this structure, there are two dielectric-plasmon supermodes with two resonance peaks separated by 50 nm. A red shift is observed when the refractive index of the cladding material increases. The cladding material includes water (n = 1.333) and iso-propanol solutions with refractive indices of 1.344, 1.351, and 1.365. The gold-coated ormocomp waveguide has sensitivity of about 544.55 nm/RIU with a resolution of 5.3 × 10
^-3
RIU.