Simultaneous Generation of Surface Plasmon and Lossy Mode Resonances in the Same Planar Platform.

O Fuentes,I R Matías,J M Corres,I Dominguez,I Del Villar

doi:10.3390/s22041505

Abstract

A planar waveguide consisting of a coverslip for a microscope glass slide was deposited in one of its two faces with two materials: silver and indium tin oxide (ITO). The incidence of light by the edge of the coverslip permitted the generation of both surface plasmon and lossy mode resonances (SPRs and LMRs) in the same transmission spectrum with a single optical source and detector. This proves the ability of this optical platform to be used as a benchmark for comparing different optical phenomena generated by both metal and dielectric materials, which can be used to progress in the assessment of different sensing technologies. Here the SPR and the LMR were compared in terms of sensitivity to refractive index and figure of merit (FoM), at the same time it was demonstrated that both resonances can operate independently when silver and ITO coated regions are surrounded by different refractive index liquids. The results were supported with numerical results that confirm the experimental ones.

Highlights

Surface plasmon resonances (SPRs) and lossy mode resonances (LMRs) have been widely explored in the literature [1,2,3,4,5,6]. Both are generated under the presence of a thin film, and their utilization as a sensor depends on the thickness of the thin film, its refractive index, its extinction coefficient, the refractive index of the waveguide and the surrounding medium [7]
Another difference between LMRs and SPRs is that in LMRs the position of the resonance generated by an LMR in the optical spectrum depends directly on the thickness of the coating, which allows a simple adjustment of the wavelength [17], whilst it is not so easy to establish this relationship in the case of the SPR
It was recently demonstrated the ability to generate two independent LMRs in the same transmission spectrum by coating both faces of the coverslip [20], suggesting the possibility to generate a SPR and a LMR by deposition of a metallic thin film and a dielectric thin film. This is what will be done here: a silver and an indium tin oxide (ITO) coating will be deposited on the same substrate to generate an SPR and an LMR with a single light source and spectrometer. This will demonstrate that this setup can be used for analyzing and comparing different optical phenomena, concretely here for comparing the sensitivity and figure of merit (FoM) of an SPR and an LMR in the visible region

Summary

Introduction

Its use is beneficial for the mass production of sensors based on LMRs. The difference in the materials required for the generation of each resonance can be explained by the relation between the permittivity of the thin-film and the media surrounding it. Another difference between LMRs and SPRs is that in LMRs the position of the resonance generated by an LMR in the optical spectrum depends directly on the thickness of the coating, which allows a simple adjustment of the wavelength [17], whilst it is not so easy to establish this relationship in the case of the SPR.

Results

Conclusion