Fig. 2. Resonance of the monochromatic lights.

a Schematic model of the conjugated-BIC optical grating with the incident light projects onto the grating. The thicknesses of ITO, SnO₂, and ZEP520A are set at 50 nm, 50 nm, and 350 nm, respectively. Field distribution at the grating with the b on-resonant light and c off-resonant light. Results show that the 540-nm on-resonant light generates a strong resonance with the grating, resulting in monochromatic light confinement. Top-view SEM images of the gratings with resonant wavelength at d 455 nm, e 540 nm, and f 655 nm. Results show that tuning the grating structure can effectively adjust the wavelength of the on-resonant light. Corresponding simulated and experimental transmission spectra of the gratings with resonant wavelength at g 455 nm, h 540 nm, and i 655 nm. On-resonant lights can be effectively confined and off-resonant lights will transmit through the grating, resulting in sharp dips in the transmission spectra