Abstract
In this paper, we present and analyze a compact inner-wall grating slot microring resonator (IG-SMRR) with the footprint of less than 13 μm × 13 μm on the silicon-on-insulator (SOI) platform for label-free sensing, which comprises a slot microring resonator (SMRR) and inner-wall grating (IG). Its detection range is significantly enhanced without the limitation of the free spectral region (FSR) owing to the combination of SMRR and IG. The IG-SMRR has an ultra-large quasi-FSR of 84.5 nm as the detection range, and enlarged factor is up to over 3 compared with the conventional SMRR. The concentration sensitivities of sodium chloride solutions and D-glucose solutions are 996.91 pm/% and 968.05 pm/%, respectively, and the corresponding refractive index (RI) sensitivities are 559.5 nm/RIU (refractive index unit) and 558.3 nm/RIU, respectively. The investigation on the combination of SMRR and IG is a valuable exploration of label-free sensing application for ultra-large detection range and ultra-high sensitivity in future.
Highlights
Label-free optical sensors have been investigated extensively in many applications, such as medical diagnostics, drug detection, food security, pesticide residue detection, environmental monitoring, homeland defense, and so on
We present a compact optical label-free sensor based on inner-wall grating slot microring resonator (IG-slot microring resonator (SMRR)) to acquire the ultra-large detection range and ensure the high sensitivity
The light in the bus waveguide is filtered by SMRR at first, and the resonant light filtering processes
Summary
Label-free optical sensors have been investigated extensively in many applications, such as medical diagnostics, drug detection, food security, pesticide residue detection, environmental monitoring, homeland defense, and so on. In order to enlarge the detection range, some schemes, such as serially coupled double MRRs [15], the MRR with bent contra-directional couplers [16], Mach–Zehnder interferential couple MRR [17], grating-coupled silicon MRR [18], and angular grating MRR [19] are investigated to expand the FSR. These schemes can enlarge the FSR, but the sensitivities of the above schemes are relativity lower than the sensitivity of SMRR. We present a compact optical label-free sensor based on IG-SMRR to acquire the ultra-large detection range and ensure the high sensitivity. Taking the sodium chloride solutions and D-glucose solution as the top cladding layer, the sensing characteristics of the optical label-free sensor are demonstrated
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