Nonlinear Quasi-BIC With Non-Hermitian Polarization Phase Quantization in Sm³⁺ :BiPO₄

This study investigates quasi bound states in the continuum (qBICs) in profile and resonance signals arising from polarization phase quantization in Sm³⁺:BiPO₄. Two types of profile qBICs (third-order non-resonance profile qBIC and fourth-order resonance profile qBIC), result from destructive and constructive quantization phase, respectively. In addition, two types of third-order resonance qBICs, namely two-dark/onebright states (2D1B) and one-dark/two-bright states (1D2B), are observed at constructive and destructive channel phase, respectively. The third-order 2D1B states resonance qBIC together with two optical jump, comes from eigenvector amplitude splitting near the exceptional point (EP) due to quasi-constructive quantization phase. These findings suggest potential applications in the interference-based quantum memory devices.