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.

Optical skyrmions formed by photonic spin–orbit (SO) coupling are of significant interest in high-dimensional optical information processing. We report the formation mechanism and non-Hermitian properties of skyrmion-like states in a circular confinement potential with photonic SO coupling, which is preferably realized in a concave-planar microcavity system. We show that the effective photonic gauge field leads to two split manifolds of degenerate skyrmions whose spin textures can be controlled via the non-Hermitian properties by introducing circularly polarized gain and loss, exhibiting dramatically discrepant evolutions at the two sides of the exceptional point (EP). Furthermore, the lifetime degeneracy can be lifted by spatially inhomogeneous pumping according to the non-Hermitian mechanism, enabling the possibility for the skyrmion laser. By introducing shape asymmetry of the confinement potential, a double EP evolution can be achieved, which allows non-Hermitian control of the SO coupled states with higher degrees of freedom. These results open the way for the non-Hermitian control of photonic spin in confined systems, which would be of great significance for the fundamentals of advanced optical information processing.

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.

为了研究硅基QPD在不同能量密度、不同脉宽激光辐照下的损伤面积、形貌，基于二维显微测量技术，测量了硅基QPD单一象限的损伤面积、形貌随激光能量密度和脉宽的变化。结果表明，在毫秒脉冲激光作用下，硅基QPD产生表面剥落、褶皱、裂纹、熔坑等损伤效果，且主要受入射激光功率密度影响，损伤面积随激光能量密度逐渐增加，随脉宽增加逐渐降低。通过实测分析，得出了不同激光脉宽下，硅基QPD表面形貌损伤阈值。激光脉宽为0.5 ms，能量密度为15.79 J/cm²时，硅基QPD出现熔融损伤；而脉宽为1.0、1.5、2.0、3.0 ms时，硅基QPD出现表面剥落的能量密度值为14.12、33.94、39.76、47.62 J/cm²。

Mode distortion induced by stimulated Raman scattering (SRS) has become a new obstacle for the further development of high-power fiber lasers with high beam quality. Here, an approach for effective suppression of the SRS-induced mode distortion in high-power fiber amplifiers has been demonstrated experimentally by adjusting the seed power (output power of seed source) and forward feedback coefficient of the rear port in the seed source. It is shown that the threshold power of the SRS-induced mode distortion can be increased significantly by reducing the seed power or the forward feedback coefficient. Moreover, it has also been found that the threshold power is extremely sensitive to the forward feedback power value from the rear port. The influence of the seed power on the threshold power can be attributed to the fact that the seed power plays an important role in the effective length of the gain fiber in the amplifier. The influence of the forward feedback coefficient on the threshold power can be attributed to the enhanced SRS configuration because the end surface of the rear port together with the fiber in the amplifier constitutes a half-opening cavity. This suppression approach will be very helpful to further develop the high-power fiber amplifiers with high beam quality.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) attain increasing attention due to their exceptional nonlinear optical efficiencies, which hold promising potential for on-chip photonics and advanced optoelectronic applications. Planar TMDs have been proven to support orders-higher third-order nonlinear coefficients in comparison with common nonlinear materials. Interestingly, stronger light–matter interaction could be motivated when curved features are introduced to 2D TMDs. Here, a type of inorganic fullerene-like WS2 nanoparticles is chemically synthesized using hard mesoporous silica. By using the spatial self-phase modulation (SSPM) method, the nonlinear refractive index n2 and third-order susceptibility χ(3) are investigated in the visible range. It is found that n2～10-5cm2/W and χ(3)～10-7esu, two orders higher than the counterparts of planar WS2 structures. Our experimental findings provide a fresh thinking in designing nonlinear optical materials and endow TMDs with new potentials in photonic integration applications.