Quantized bound states in the continuum generated by the one-dimensional finite periodic ring optical waveguide networks

In this paper, the bound states in the continuum (BICs) generated by the one-dimensional (1D) finite periodic ring optical waveguide networks (FPROWNs) are investigated. It is found that by regulating the length ratio of the upper arm to the lower one of the rings the FPROWNs can produce the symmetry -protected -bound (SPB) and the accidental -extended (AE) types of BICs, and the angular frequencies of both BICs are quantized. Furthermore, the quasi-BICs exhibit exponentially increasing ultra -high Q factors, and the maximal Q factor in this work arrives at 1.66 x 109, which is on the same order of magnitude of the best results reported so far. Moreover, it is also found that the quasi-BICs produced by the FPROWNs are all formed by the intermediatestate photons. This work may not only deepen the understanding of BIC but also possess potential applications in highly sensitive sensors, narrow -band filters, and BIC lasers, etc.