Nanofluidic Refractive-Index Sensors Formed by Nanocavity Resonators in Metals without Plasmons

Shih-Pin Tsai,Ding-Wei Huang,Yao-Feng Ma,Ming-Je Sung

doi:10.3390/s110302939

Abstract

Nanocavity resonators in metals acting as nanofluidic refractive-index sensors were analyzed theoretically. With the illumination of transverse electric polarized light, the proposed refractive index sensor structure acts as a pure electromagnetic resonator without the excitation of surface plasmons. The reflected signal from the nanocavity resonators can be very sensitive to the refractive index of the fluids inside the nanocavities due to the enhancement of the electric field of the resonant mode inside the cavities. Such a sensor configuration can be a useful tool for probing the refractive index change of the fluid inside the nanocavities using the spectral, angular or intensity interrogation schemes. The wavelength sensitivity of 430 nm/RIU, angular sensitivity of 200–1,000 deg/RIU and intensity sensitivity of 25.5 RIU−1 can be achieved in the proposed sensor configuration.

Highlights

Nanostructured metals which utilize the excitation of surface plasmons have been widely used as facilitating tools for probing surface interactions [1,2] and enhancing the nonlinear effects near metal surfaces [3], the enhancement of the electric fields in some nanostructured metals without plasmons have been reported for enhancing the transmission of light [4], reducing the reflection of light [5], or enhancing the absorption of light in metal nanostructures [6]
With the illumination of transverse electric (TE) polarized light, the proposed structures act as pure electromagnetic cavity resonators without the excitation of surface plasmons
According to the results of our study, such a refractive index sensor configuration based on nano-cavity resonators can be a useful tool for probing the refractive index change of the fluid using the spectral, angular or intensity interrogation schemes

Summary

Introduction

Nanostructured metals which utilize the excitation of surface plasmons have been widely used as facilitating tools for probing surface interactions [1,2] and enhancing the nonlinear effects near metal surfaces [3], the enhancement of the electric fields in some nanostructured metals without plasmons have been reported for enhancing the transmission of light [4], reducing the reflection of light [5], or enhancing the absorption of light in metal nanostructures [6] In this context, the use of Sensors 2011, 11 nano-cavity resonators in metals as refractive index sensors was proposed and studied. The feasibility of using the proposed nano-cavity resonators in metals as refractive index sensors and the performance of such a sensor configuration were evaluated

Design and Experiments

Result and Discussion

Conclusions