Large area implementation of bound states in the continuum in a one-dimensional photonic crystal by an optical axis rotating approach.

It is generally accepted that the bound states in the continuum (BICs) are usually realized in a one-dimensional system by the TM-polarized light incident at Brewster's angle. However, the optimal BICs can be achieved only under specific incident light and at a specific polarization incident angle, which poses challenges to its experimental implementation. Serving this purpose, we design a system composed of an anisotropic material (AM) embedded in one-dimensional photonic crystals (1D-PhCs), demonstrating that both TE and TM waves can realize BICs. Moreover, the existence of BICs does not hinge on the specific angle of the incident light. In contrast to the traditional methods of creation system symmetry to achieve symmetry-protected BICs (SP-BICs), we use the 1D-PhC to confine the TE or TM wave in different frequencies first as a form of cavity (localized) mode and rotating the optical axis of AM at a specific angle to realize the field mismatch. Besides, our system can realize Friedrich-Wintgen BICs (FW-BICs) because of the destructive interference of the radiative waves in other specific angles, which can be detected as some Fano resonance collapsing points in reflection spectra. Our results provide more flexible conditions for the realization of BICs under the TE-polarized light, making the implementation of switch Q-factor easier.