Abstract:
Bound states in the continuum (BIC) is a peculiar resonant mode with an infinite radiative
lifetime and quality factor (Q-factor) embedded within the radiation continuum, which find
applications in sensing, lasing, and quantum photonics. While an ideal BIC with an infinite
Q-factor can only occur in theory, observing quasi-BIC in realistic samples with finite sizes is
possible. However, the robustness of quasi-BIC depends primarily on the trapped
electromagnetic modes. Here, we discuss the polarization dependence and the nature of
quasi-BIC mode in a two-dimensional array of gallium arsenide (GaAs) scatterers through finite
difference time domain simulations and analytical calculations. The calculated angle- and
polarization-dependent transmission spectra show quasi-BIC evolution with high Q-factor at
near-normal incidence only for transverse magnetic polarization. The calculated total scattering
cross-section implies the dominant contribution from electric dipole moments in generating the
quasi-BIC. The evolution of quasi-BIC mode is discussed in terms of Mie or Fabry–Perot
modes using geometry-dependent transmission and field intensity calculations. The proposed
GaAs metasurfaces with quasi-BIC at 638 nm, corresponding to the zero phonon line of
nitrogen-vacancy centers in diamond are useful for applications in photonic quantum
technologies.
