In this paper, a high-sensitivity refractive index sensor based on a hybrid plasma waveguide and metal-insulator-metal waveguide combined third-order runway series mosaic microring resonator is proposed. In this structure, a GaAs waveguide ring surrounds a gold waveguide ring in the middle, and the innermost layer is a disk made of gold material.The outer groove waveguide is composed of GaAs-air-alloy, and the inner groove waveguide is made of the Gold-Air-Gold material disc. By filling different substances in the groove, the change of refractive index will affect the optical signal strength of the output spectrum. The finite element method simulates the transmission spectrum and electric field distribution of the sensor structure. The amplitude coupling coefficient and attenuation factor affecting the resonator's performance are analyzed, and the structural parameters of the slot waveguide are optimized. The numerical simulation results show that the sensor quality factor of this structure is 1.54 Â 10 4 , the sensitivity is 1.2 Â 10 3 nm/RIU which is about 1.5 times higher than that of the Si ring with the same structure, the detection limit can reach 8.1892 Â 10 À7 RIU, and the free spectral range can reach 109 nm. Compared with the traditional microring structure, this microring has higher design freedom and free spectral range and is more suitable for producing biosensors with high sensitivity, low detection limit, and multi-parameter measurement.
An embedded microring resonator model using PtS2 as the core layer was designed and optimized for sensing. The inner layer is made of PtS2, and SiO2 and Si3N4 are used as cladding. The overall structure is Si3N4-SiO2-PtS2-SiO2-Si3N4. Field strength distribution of longitudinal section of single straight waveguide and the longitudinal section of coupling part of straight and annular waveguides are simulated according to the coupled-mode theory. The transfer matrix method is used to analyze characteristics between the length of the U-shaped feedback waveguide and the circumference of microring and the change of attenuation factor and coupling coefficient on the output spectrum. The simulation results showed that the embedded microring resonator with PtS2 as the core presents excellent optical properties. The resonance depth is more than –50 dB, and the sensitivity can reach 1806.61 dB/RIU. When the resonance wavelength is 1550.86 nm and the self-coupling coefficient is 0.9849. The corresponding detection limit is about 1.66056 × 10–7 dB/RIU, and the quality factor is 2.8848 × 10–5 under the measurement system with a signal-to-noise ratio of 30 dB. Compared with the traditional single microring structure, the proposed microring presents a higher free spectral range and more suitable for the fabrication of high-sensitivity, low-detection limit, and large-measurement range sensors.
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