Optimization of Silicon Nitride Waveguide Platform for On-Chip Virus Detection.

Raghi S El Shamy,Xun Li,Mohamed A Swillam

doi:10.3390/s22031152

Raghi S El Shamy, Xun Li + Show 1 more

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https://doi.org/10.3390/s22031152

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Abstract

This work presents a rigorous and generic sensitivity analysis of silicon nitride on silicon dioxide strip waveguide for virus detection. In general, by functionalizing the waveguide surface with a specific antibodies layer, we make the optical sensor sensitive only to a particular virus. Unlike conventional virus detection methods such as polymerase chain reaction (PCR), integrated refractive index (RI) optical sensors offer cheap and mass-scale fabrication of compact devices for fast and straightforward detection with high sensitivity and selectivity. Our numerical analysis includes a wide range of wavelengths from visible to mid-infrared. We determined the strip waveguide’s single-mode dimensions and the optimum dimensions that maximize the sensitivity to the virus layer attached to its surface at each wavelength using finite difference eigenmode (FDE) solver. We also compared the strip waveguide with the widely used slot waveguide. Our theoretical study shows that silicon nitride strip waveguide working at lower wavelengths is the optimum choice for virus detection as it maximizes both the waveguide sensitivity (Swg) and the figure of merit (FOM) of the sensor. The optimized waveguides are well suited for a range of viruses with different sizes and refractive indices. Balanced Mach–Zehnder interferometer (MZI) sensors were designed using FDE solver and photonic circuit simulator at different wavelengths. The designed sensors show high FOM at λ = 450 nm ranging from 500 RIU−1 up to 1231 RIU−1 with LMZI = 500 µm. Different MZI configurations were also studied and compared. Finally, edge coupling from the fiber to the sensor was designed, showing insertion loss (IL) at λ = 450 nm of 4.1 dB for the design with FOM = 500 RIU−1. The obtained coupling efficiencies are higher than recently proposed fiber couplers.

Highlights

The coronavirus disease pandemic of 2019 (COVID-19) is currently an exceptional threat to human lives all over the world
Such behavior is expected large waveguide widths, most theand mode field is width is close to For the mode cut-off width
We propose a Si3 N4 strip waveguide to be used as the sensing arm in different integrated optical sensors configurations for virus detection

Summary

Introduction

The coronavirus disease pandemic of 2019 (COVID-19) is currently an exceptional threat to human lives all over the world. Its expeditious spread has led to millions of cases and hundreds of thousands of deaths in a few months. Almost all countries worldwide were forced to lockdown for several months to limit the spread of the virus, leading to devastating social and economic effects. Polymerase chain reaction (PCR) is one of the well-known methods used for virus detection and it is the primary method used currently for COVID-19 detection [2]. This technique is highly sensitive and accurate, it is expensive, time-consuming, and involves complex procedures and sample preparation

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