Quasi-bound states in the continuum enhanced tunable second-harmonic generation of dimer dielectric metasurfaces

Bound states in the continuum (BIC) offer a promising prospect for achieving high-quality resonances within dielectric metasurfaces, which can significantly enhance optical nonlinear processes. In this study, we investigate the enhancement of second-harmonic generation (SHG) using quasi-BIC with tunable resonance wavelengths and conversion efficiency, and the BIC resonance properties were studied by introducing symmetrical radius or gap perturbations into the dimer metasurfaces. It is found that the SHG efficiency in Al 0.18 Ga 0.82 As could be enhanced by two orders in magnitude compared to previous studies by utilizing the quasi-BIC in dimer arrays. The proposed system also demonstrated the ability to tune resonance wavelengths by altering the size parameters of the dimer unit cell. The exceptional tunability of the designed system’s resonance wavelengths and Q-factors opens up new possibilities for enhancing light-matter interaction and developing efficient SHG devices.