Observation of an Optical Bound State in Photonic Crystal Slabs with U-Shape Nanohole Array

We have theoretically investigated the reflectance spectrums of the U-shape nanohole symmetry and asymmetric structure. It is shown that light can be perfectly confined in the photonic crystal slab at a given incident angle. Also, we studied the influence of U-shape nanohole size on reflectance spectrum and Q-factor of both at- Γ bound states in the continuum (BIC) and off- Γ BIC with the nanohole shape in symmetrical and asymmetrical cases. For a U-shape nanohole symmetry structure, it is shown that at- Γ BIC is dependent on the nanohole size. The Q-factor of the nanoholes structure at off- Γ BIC can reach the order of 10 6 . The obtained results provide useful guidelines for practical implementations of biosensing, perfect filters and waveguides.