Design analysis of doped-silicon surface plasmon resonance immunosensors in mid-infrared range

William Dipippo,Keunhan Park,Bong Jae Lee

doi:10.1364/oe.18.019396

William Dipippo, Keunhan Park + Show 1 more

Open Access

https://doi.org/10.1364/oe.18.019396

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Abstract

This paper reports the design analysis of a microfabricatable mid-infrared (mid-IR) surface plasmon resonance (SPR) sensor platform. The proposed platform has periodic heavily doped profiles implanted into intrinsic silicon and a thin gold layer deposited on top, making a physically flat grating SPR coupler. A rigorous coupled-wave analysis was conducted to prove the design feasibility, characterize the sensor's performance, and determine geometric parameters of the heavily doped profiles. Finite element analysis (FEA) was also employed to compute the electromagnetic field distributions at the plasmon resonance. Obtained results reveal that the proposed structure can excite the SPR on the normal incidence of mid-IR light, resulting in a large probing depth that will facilitate the study of larger analytes. Furthermore, the whole structure can be microfabricated with well-established batch protocols, providing tunability in the SPR excitation wavelength for specific biosensing needs with a low manufacturing cost. When the SPR sensor is to be used in a Fourier-transform infrared (FTIR) spectroscopy platform, its detection sensitivity and limit of detection are estimated to be 3022 nm/RIU and ~70 pg/mm(2), respectively, at a sample layer thickness of 100 nm. The design analysis performed in the present study will allow the fabrication of a tunable, disposable mid-IR SPR sensor that combines advantages of conventional prism and metallic grating SPR sensors.

Highlights

A surface plasmon is a localized electromagnetic (EM) wave that propagates along the metaldielectric interface and exponentially decays into both media [1]
This paper reports the design analysis of a mid-IR surface plasmon resonance (SPR) sensor that resolves the aforementioned issues of current SPR platforms and can be fabricated using readily available mircoelectromechanical system (MEMS) processes
In order to demonstrate the feasibility of the doped-Si SPR coupler, Fig. 2(a) shows the dispersion relation of the SPR excitation through the modulation of both vacuum wavelength and incidence angle, and Fig. 2(b) shows the reflectance spectrum for different incidence angles

Summary

Introduction

A surface plasmon is a localized electromagnetic (EM) wave that propagates along the metaldielectric interface and exponentially decays into both media [1]. The use of a longer wavelength as a light source excites surface plasmons that have a larger penetration depth into a sample side [7] and experience less scattering during propagation along the interface [8], which will allow the accurate detection of the SPR dip position for larger samples, such as living cells [2]. Another advantage is that most biological specimens are practically transparent upon exposure to mid-IR radiation. The performance analysis is conducted when the proposed sensor is integrated with the Fourier transform infrared (FTIR) spectroscopy, which would significantly reduce the instrumentation cost

Modeling

Results and discussion

Conclusion