Engineering of the orbital angular momentum (OAM) of light due to interaction with photonic lattices reveals rich physics and motivates potential applications. We report the experimental creation of regularly distributed quantized vortex arrays in momentum space by probing the honeycomb and hexagonal photonic lattices with a single focused Gaussian beam. For the honeycomb lattice, the vortices are associated with Dirac points. However, we show that the resulting spatial patterns of vortices are strongly defined by the symmetry of the wave packet evolving in the photonic lattices and not by their topological properties. Our findings reveal the underlying physics by connecting the symmetry and OAM conversion and provide a simple and efficient method to create regularly distributed multiple vortices from unstructured light.

研究了一种基于非线性光纤环形镜“8”字形谐振腔结构的波长可调谐被动锁模掺铒光纤激光器，该激光器通过将偏振控制器加在耦合比为30/70的2×2光纤耦合器首尾相连的环内，在整个谐振腔的右端搭建了一个Sagnac环形滤波器。当泵浦功率为270 mW时，锁模光纤激光器输出了中心波长为1 555.7 nm的传统孤子，其光谱的3-dB带宽为4.2 nm，重复频率为21.1 MHz，信噪比为68 dB，脉冲宽度为0.759 ps。此外，在不改变腔内其他器件的情况下只增加泵浦功率，实现了锁模光纤激光器的连续可调谐，中心波长的调谐范围为1.5 nm；在增加泵浦功率到360 mW时，调节偏振控制器出现了松束缚态孤子。

By taking advantage of the optical induction method, a non-Hermitian photonic graphene lattice is efficiently established inside an atomic vapor cell under the condition of electromagnetically induced transparency. This non-Hermitian structure is accomplished by simultaneously modulating both the real and imaginary components of the refractive index into honeycomb profiles. The transmitted probe field can either exhibit a hexagonal or honeycomb intensity profile when the degree of non-Hermiticity is effectively controlled by the ratio between imaginary and real indices. The experimental realization of such an instantaneously tunable complex honeycomb potential sets a new platform for future experimental exploration of non-Hermitian topological photonics. Also, we demonstrate the Talbot effect of the transmitted probe patterns. Such a self-imaging effect based on a non-Hermitian structure provides a promising route to potentially improve the related applications, such as an all-optical-controllable Talbot–Lau interferometer.

CVD金刚石是一种性能优异的红外光学窗口材料，但其在红外波段的理论透过率仅能实现约71%。通过表面亚波长结构设计可进一步增强CVD金刚石膜的光学透过性能。该研究首先通过理论模拟，建立了金刚石微结构特征与光学增透之间的定量关系。基于此为指导，探讨了在具有微结构硅片表面，采用MPCVD方法复制生长出具有微结构的金刚石自支撑光学级薄膜，用于提升金刚石膜在红外波段的透过率。采用扫描电镜（SEM）观察了原始硅片和金刚石表面及微结构形貌，通过拉曼散射光谱评估了金刚石的生长质量及形核层影响，采用红外光谱仪测试了金刚石红外透过率。结果显示，单面构筑微结构后，金刚石膜在8~12 μm波段的透过率可从70%提升至76%，说明表面微结构能显著提升金刚石膜的光学透过性能。非金刚石形核层以及表面微结构的完整性不足可能是导致实验结果与理论模拟结果具有一定偏差的主要原因。