Enhancement of Long-Range Surface Plasmon Excitation, Dynamic Range and Figure of Merit Using a Dielectric Resonant Cavity

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.

Quantitative Cross-Platform Performance Comparison between Different Detection Mechanisms in Surface Plasmon Sensors for Voltage Sensing

“…Another approach to compare this sensitivity is to compare it with bulk refractive index sensitivity as if this 47 nm was employed as a conventional SPR sensor to measure the change in the refractive index of the sample [ 14 ]. In other words, n 1 and n 2 were identical and the refractive index of n 3 were varied until the change in or of 1.16 × 10 −5 rad/nm was reached.…”

“…It is worth pointing out that some of the measurement mechanisms do not rely on the intensity of the dip, but rely mostly on how much the dip moves, such as interferometric detection [ 14 ]. If these techniques were implemented, it is therefore better to align the optical system for wavelength coupling measurement since it has the higher sensitivity compared to angular measurement.…”

“…The FoM term takes into account (1) how much the SPR dip moves and (2) how narrow the SPR dip is. This has been widely accepted as a standard performance parameter for biosensors [ 14 ]. …”

“…The fluorescence labelling also suffers from photobleaching, making a long run experiment not practical [ 13 ]. The microfiber approach requires the microfiber to be placed very close to the sample, making the optical alignment difficult and the microfiber also obscures the sample accessibility [ 14 ].…”

Analysis of Open Grating-Based Fabry–Pérot Resonance Structures With Potential Applications for Ultrasensitive Refractive Index Sensing

“…F W H M  (6) (iv) Dynamic range (DR) is the numerical value indicating the range of refractive indices, which the sensor can measure under defined conditions; the reflectance at the minimum reflectance dip of a mode must be less than 0.25 [27]. The refractive index sensing capability of the proposed open grating based FP resonator is quantified compared to the conventional FP resonator shown in Fig.…”