Analogue of electromagnetically induced transparency in all-dielectric metasurface induced by quasi-bound state in the continuum for switching

We design and numerically investigate an all-dielectric metasurface composed of ring/disk cavity supporting quasi-bound state in the continuum (BIC) by breaking the in-plane symmetry of the cavity through removing a part from the edge of the central disk that invokes a leakage channel in the form of weakly radiating electromagnetically induced transparency. Far-field radiations and near-field distributions explain the evolution from BIC to quasi-BIC and further point out the dominant magnetic quadrupole component in quasi-BIC. Such quasi-BIC can be switched on and off at orthogonal polarizations and modulated by the intrinsic material loss. Further, we compare the effects of quasi-BICs excited by the offset and removing a part from the edge of the central disk on Q-factors and near-field enhancement, which can be tailored and optimized by selecting the appropriate degree and way of asymmetry.