Fig. 1. Schematic of device. (a) Schematic of top-layer waveguide coupled with bottom-layer resonator; (b) schematic of sub-microring coupled with bottom-layer U-bend waveguide; (c) schematic of single sub-microring resonance filter; (d) schematic of double sub-microring resonance filter

Fig. 2. Output spectra of device under different k₁ and fixed k₂

Fig. 3. Output spectra of single sub-microring device under different phases of racetrack resonator

Fig. 4. Output spectra of double sub-microring device under different k₁ and fixed k₂

Fig. 5. Output spectra of double sub-microring device under different phases of racetrack resonator

Fig. 6. Physical image of single sub-microring device

Fig. 7. Physical installation image of test system (inset is enlarged coupling part)

Fig. 8. Output spectra of single sub-microring device under different coupling lengths

Fig. 9. Output spectrum of single sub-microring device versus applied voltage

Fig. 10. Physical image of double sub-microring device

Fig. 11. Output spectra of device under different coupling lengths

Fig. 12. Output spectrum of double sub-microring device versus applied voltage

Fig. 13. Resonance wavelength of output spectrum versus applied voltage

Fig. 14. Output spectral comparison between double sub-microring device and single sub-microring device