Bimetallic-waveguide coupled sensors for tunable plasmonic devices

Abstract

Surface plasmon resonance (SPR) has been a widely used optical technique for the real time and label free sensing applications in biomedicine, homeland security, food safety, environmental monitoring, etc. Surface plasmons (SPs) being extremely sensitive to the surrounding media, their characteristics can be modulated by tuning their dielectric environment. The unique property of the nematic liquid crystalline materials that their dielectric constant can be tuned by externally applied electric fields formed the basis for development of tunable plasmonic sensor for monitoring changes at metal/dielectric interfaces. Even though sensors with high sensitivity are available, it remains highly desirable to enhance sensor resolution and evanescent fields for many such applications. Through computer simulations and SPR measurements, we have investigated SPR sensor architectures fabricated with single metallic, bimetallic, and bimetallic-waveguide coupled (Bi-WC) thin film structures. We present evidence for substantial enhancements in; resolution, sensitivity and decay length of evanescent fields from the developed Bi-WC SPR structures. A unique fixed detector Kretschman configuration optical system is employed, which is capable of carrying out pump-probe spectroscopy for simultaneous measurements of SPR related effects on PL characteristics of semiconductor quantum dots. Detailed results from these investigations will be presented and discussed.