Characteristics of stacked multi-slot ring resonator sensors

Abstract

Purpose This paper aims to develop ring resonator type optical sensors for high-sensitive detection of biomaterials and a solution concentration surrounding sensor devices. The sensing characteristics of a proposed device are investigated. Design/methodology/approach The proposed device structure is multi-slot ring resonator where the horizontal slots are arranged in vertical direction called as stacked multi-slot ring resonator. The ring resonator consists of silicon nitride because of several advantages such as easy integration of Si photo-detectors. A high sensitivity is expected in this structure because the slot height is precisely controlled by the thickness of stacked silicon nitride and etched silicon oxide layers. Sensing characteristics are evaluated from the simulated effective refractive index using the finite element method and sucrose solution sensing is confirmed using polydimethylsiloxane fluid channel. Findings In the simulation for the solution concentration sensor, the detection sensitivity is enhanced with increasing the slot height and the number of slots. On the other hand, for the biomaterial sensor such as the adsorbed antigen-antibody reaction, the sensitivity increases with decreasing the slot height. In this case, more than four times higher sensitivity is expected compared with the slot ring resonator sensor with vertical single slot and 0.1-0.2 μm slot width. Originality/value This paper presents an improved new structure of ring resonator type sensors and its optimum design parameters. The sensing characteristics are evaluated, and, for the biomaterial sensor, the sensitivity is high in comparison to the previous slot ring resonator.