Cascaded microring resonator configuration with inbuilt tapered regions for simultaneous detection of assorted nanoparticles

Fast and accurate detection of nanoparticles (NP) has always been challenging due to the weak interaction of nanoparticles with the transducing signal. Moreover, detecting nanoparticles of different sizes and types mixed in a matrix adds more difficulty. In this work, we propose an integrated on-chip photonic platform that can detect a single nanoparticle. The proposed device comprises two parallel-coupled microring resonators where a small region in the noncoupled arms of the resonator has been tapered. Tapered regions intensify the evanescent field strength by many folds, which improves light-matter interaction, resulting in better sensitivity. Finite difference time domain simulations reveal the splitting of a resonant mode in the presence of a gold nanoparticle (AuNP) of radius 100 nm, whereas in the case of dielectric NP, broadening in linewidth is observed. The proposed approach has the unique capability to detect various sizes and types of NP simultaneously, including dielectric nanoparticles. Therefore, the proposed architecture may play a pivotal role in the simultaneous quantification and identification of biological objects such as novel viruses, bacteria, and proteins.