ABSTRACT
This work presents a rigorous sensitivity analysis of silicon nitride on silicon dioxide strip waveguide for virus detection, focusing on COVID-19. In general, by functionalizing the waveguide surface with 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 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. We also compared the strip waveguide to the widely used slot waveguide. Our 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 (S wg ) and the figure of merit (FOM) of the sensor. Furthermore, the optimized waveguide can work for a range of viruses. Balanced Mach-Zehnder interferometer (MZI) sensors were designed at different wavelengths showing high FOM at λ = 450nm ranging from 500 RIU -1 up to 1231 RIU -1 with L MZI =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 = 450nm of 4.1 dB for the design with FOM = 500 RIU -1 . The obtained coupling efficiencies are higher than recently proposed fiber couplers.