Prospects for photon–phonon dressing and crystal-field non-Hermitian alignment of Eu3+:BiPO4†

Non-Hermitian alignment has recently emerged as a rapidly developing field due to its exotic characteristics related to energy level systems, where the dressing plays a critical role. The photon and phonon are coupled at different energy levels to achieve the energy level alignment. Our observations indicate that strong destructive quantization occurs at large polarization angles, resulting in a strong dip alignment in the fluorescence (FL) region, attributed to large decay rates. In contrast, strong constructive quantization at small polarization angles results in flat linear and circular peak alignment in the spontaneous four wave mixing (SFWM) region due to a small decay rate. Notably, the linear dressing quantization exceeds the circular dressing quantization at an intermediate polarization angle, leading to more substantial linear alignment compared to circular alignment. Moreover, Eu³⁺:BiPO₄ with weak phonon detuning and stronger phonon dressing quantization has strong constructive alignment in SFWM and strong destructive alignment in fluorescence (FL) as compared to Eu³⁺:NaYF₄. Such destructive and constructive alignment indicates significant potential for developing a spectral homogenizer with 96% efficiency to produce 24 nm spectral alignment.