Optical Ring Resonators: A Platform for Biological Sensing Applications.

Rapid advances in biochemistry and genetics lead to expansion of the various medical instruments for detection and prevention tasks. On the other hand, food safety is an important concern which relates to the public health. One of the most reliable tools to detect bioparticles (i.e., DNA molecules and proteins) and determining the authenticity of food products is the optical ring resonators. By depositing a recipient polymeric layer of target particle on the periphery of an optical ring resonator, it is possible to identify the existence of molecules by calculating the shift in the spectral response of the ring resonators. The main purpose of this paper is to investigate the performance of two structures of optical ring resonators, (i) all-pass and (ii) add-drop resonators for sensing applications. We propose a new configuration for sensing applications by introducing a nanogap in the all-pass ring resonator. The performance of these resonators is studied from sensing point of view. Simulation results, using finite difference time domain paradigm, revealed that the existence of a nanogap in the ring configuration achieves higher amount of sensitivity; thus, this structure is more suitable for biosensing applications.