Analysis of integrated silicon nitride lab-on-a-chip optofluidic sensor at visible wavelength for absorbance based biosensing applications

This work focuses on the analysis of a Silicon Nitride (Si3N4) lab-on-a-chip optofluidic biosensor at visible wavelength. The major design components considered for optimization are the patterned Si3N4 waveguide and the rectangular photonic crystal. The structure is designed on Si3N4 on insulator substrate. The analysis is carried out at a wavelength of 660 nm. The Photonic Crystal (PC) having lattice constant of 300 nm with radius 130 nm is placed on etched Silicon Nitride layer. The analytes considered for optofluidic sensor analysis have properties comparable to those of human blood. The analysis is carried out with the aid of modal analysis and Finite-Difference Time-Domain (FDTD) approach. The modal analysis yields effective refractive index in the range from 1.6985 to 1.8234 for different constituents of human blood. The sensitivity is determined based on power absorbance and refractive index of the complete structure. This work reports a refractive index-based sensitivity of ∼2.5×10−10 RIU (Refractive Index Unit) and Q-factor (quality factor) of 8.39667×104. Transmittance and sensitivity are determined for the visible wavelength range cantered at 660 nm. Such sensors can be used as absorbance-based sensing devices.