Double slot micro ring resonators with inner wall angular gratings as ultra-sensitive biochemical sensors

• Published in: Optics express 2023-06, Vol.31 (12), p.20034-20048
• Main Authors: Cheng, Weiqing, Sun, Xiao, Ye, Shengwei, Yuan, Bocheng, Xiong, Jichuan, Liu, Xuefeng, Sun, Yiming, Marsh, John H, Hou, Lianping
• Format: Article
• Language: English
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.483990

We simulate and demonstrate experimentally an inner-wall grating double slot micro ring resonator (IG-DSMRR) with a center slot ring radius of only 6.72 µm based on the silicon-on-insulator platform. This novel photonic-integrated sensor for optical label-free biochemical analysis boosts the measured refractive index (RI) sensitivity in glucose solutions to 563 nm/RIU with the limit of detection value being 3.7 × 10 RIU (refractive index units). The concentration sensitivity for sodium chloride solutions can reach 981 pm/%, with a minimum concentration detection limit of 0.02%. Using the combination of DSMRR and IG, the detection range is enlarged significantly to 72.62 nm, three times the free spectral range of conventional slot micro ring resonators. The measured Q-factor is 1.6 × 10 , and the straight strip and double slot waveguide transmission losses are 0.9 dB/cm and 20.2 dB/cm, respectively. This IG-DSMRR combines the advantages of a micro ring resonator, slot waveguide, and angular grating and is highly desirable for biochemical sensing in liquids and gases offering an ultra-high sensitivity and ultra-large measurement range. This is the first report of a fabricated and measured double-slot micro ring resonator with an inner sidewall grating structure.