Opt Express. 2023 Jan 16;31(2):2112-2119. doi: 10.1364/OE.481141.
Coherent perfect absorption-lasing (CPAL) and collimation have been intensively studied for normal and small angle wave incidence. Here, we report a two-dimensional non-Hermitian photonic crystal for broad-angle CPAL and super-collimation. The synergy of a nonsymmorphic glide symmetry of the lattice, gain-loss modulation and an optimization of unit cell induces a parity-time phase transition in the band structure along the Brillouin zone boundary. The transition points, i.e., the exceptional points, form a slab-like contour, with nearly zero dispersion in both real and imaginary parts of the band structure. Such dispersionless band structure significantly enhances the range of incident angle for CPAL and collimation.
相干完美吸收激射（CPAL）和准直已被广泛研究用于正常和小角度波的入射。在这里，我们报告了一种二维非厄米光子晶体，用于宽带角 CPAL 和超准直。晶格的非对称滑移对称、增益-损耗调制以及单元的优化协同作用，在布里渊区边界的能带结构中诱导出了奇偶时间相位转变。转变点，即异常点，形成了板状轮廓，在能带结构的实部和虚部中几乎具有零色散。这种无弥散的能带结构显著提高了 CPAL 和准直的入射角范围。
