Abstract
In this paper, we report a theoretical framework on the effect of multiple resonances inside the dielectric cavity of insulator-insulator-metal-insulator (IIMI)-based surface plasmon sensors. It has been very well established that the structure can support both long-range surface plasmon polaritons (LRSPP) and short-range surface plasmon polaritons (SRSPP). We found that the dielectric resonant cavity under certain conditions can be employed as a resonator to enhance the LRSPP properties. These conditions are: (1) the refractive index of the resonant cavity was greater than the refractive index of the sample layer and (2) when light propagated in the resonant cavity and was evanescent in the sample layer. We showed through the analytical calculation using Fresnel equations and rigorous coupled wave theory that the proposed structure with the mentioned conditions can extend the dynamic range of LRSPP excitation and enhance at least five times more plasmon intensity on the surface of the metal compared to the surface plasmon excited by the conventional Kretschmann configuration. It can enhance the dip sensitivity and the dynamic range in refractive index sensing without losing the sharpness of the LRSPP dip. We also showed that the interferometric modes in the cavity can be insensitive to the surface plasmon modes. This allowed a self-referenced surface plasmon resonance structure, in which the interferometric mode measured changes in the sensor structure and the enhanced LRSPP measured changes in the sample channel.
Highlights
Surface Plasmon Resonance (SPR) has been a powerful scientific tool for biological protein kinetic studies [1,2,3,4]
It has been very well established that double plasmonic metal interfaces such as: (1) insulatormetal-insulator (IMI) structures [8] or (2) metal-insulator-metal (MIM) structures [9,10,11] can support two plasmonic modes, so-called, long-range surface plasmon polaritons (LRSPP) and short-range surface plasmon polaritons (SRSPP) [12]
The LRSPP mode has several preferable features over the SRSPP mode including (1) it can be excited at a lower incident k-vector and (2) it has a higher figure of merit (FoM)
Summary
Surface Plasmon Resonance (SPR) has been a powerful scientific tool for biological protein kinetic studies [1,2,3,4]. It has been very well established that double plasmonic metal interfaces such as: (1) insulatormetal-insulator (IMI) structures [8] or (2) metal-insulator-metal (MIM) structures [9,10,11] can support two plasmonic modes, so-called, long-range surface plasmon polaritons (LRSPP) and short-range surface plasmon polaritons (SRSPP) [12]. These LRSPP and SRSPP modes have been experimentally verified by several groups including Lee et al [13] and Slavík et al [14].
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