Fig. 1. Schematic diagram of the structure of silicon-based micro-ring current sensor

Fig. 2. Simulation models and transmission spectrum of micro-ring resonator. (a)(b) Simulation models; (c) transmission spectrum

Fig. 3. Change of FSR and quality factor with the radius of micro-ring

Fig. 4. SEM of the micro-ring resonators with three radii and the grating coupler. (a) Silicon based micro-ring resonator with radius of 5 μm; (b) silicon based micro-ring resonator with radius of 10 μm; (c) silicon based micro-ring resonator with radius of 15 μm; (d) grating coupler

Fig. 5. A micrograph of the micro-ring resonator coated with Fe₃O₄ magnetic nanoparticles

Fig. 6. Schematic diagram of test system structure

Fig. 7. Transmission spectra of sensors with different radii. (a) Radius of 5 μm; (b) radius of 10 μm; (c) radius of 15 μm

Fig. 8. Change of the response spectra of the sensor with the current amplitude when the radius is 5 μm

Fig. 9. Variation of resonance wavelength drift with square of current amplitude and its linear fitting under different radii

Fig. 10. Variation of resonance wavelength drift with square of current frequency and its linear fitting under different radii