Ni‐rich layered oxides have been intensively considered as promising cathode materials for next‐generation Li‐ion batteries. Nevertheless, the performance degradation caused by intergranular cracks and electrode/electrolyte interface parasitic reactions restricts their further application. Compared with secondary particles, single‐crystal (SC) materials have better mechanical integrity and cycling stability. However, the preparation of ultrahigh‐nickel layered SC cathode still remains a serious challenge. Herein, a novel LiOH‐LiNO₃‐H₃BO₃ molten‐salt method is proposed to synthesize SC LiNi_0.92Co_0.06Mn_0.02O₂ with considerable crystallinity and uniformity. The critical impacts of calcination temperature and boric acid on the microstructure and electrochemical property of Ni‐rich layered oxides are systematically investigated. The results show that the crystal growth is promoted and the stability of crystal structure is improved by this synthesis method. In particular, the optimal electrode demonstrates a superior initial discharge capacity of 214.8 mAh g^–1 with a high capacity retention of 86.3% over 300 cycles as tested by pouch‐type full cells at 45 ºC. This work not only prepares an ultrahigh‐nickel layered CS cathode with superior electrochemical performances, but also provides a feasible method for the synthesis of other CS layered cathode materials.

Fork-shaped fringes are formed for off-axis interference between two oblique-incident vortex beams. New formulas considering various parameters [such as the angles between two vortex beams and their topological charges (TCs)] are established to describe all kinds of fork-shaped fringes. An improved Mach–Zehnder interferometer is employed to investigate these interference fringes. Experimental measurements are consistent with numerical simulations by using our formulas. Our results broaden the understanding of the off-axis interference between two vortex beams, and can be applied to detect the TCs’ sign and value of an unknown vortex beam, especially large-value TCs.

Halide perovskite quantum dots (PQDs) have exhibited significantly superior nonlinear optical properties compared to traditional semiconductor materials thanks to their peculiar physical and electronic structures. By further improving the nonlinear optical properties of PQDs, it is expected to adapt to ultrafast photonics applications. This work reported the nonlinear optical properties of methylammonium lead bromide‐graphene (CH ₃ NH ₃ PbBr ₃ ‐G) composites synthesized by growing CH ₃ NH ₃ PbBr ₃ quantum dots directly from a graphene oxide lattice. Our experiments indicate that the combined advantages of the ultrafast charge transport properties from graphene and the strong charge generation efficiency of perovskite can be integrated together. The CH ₃ NH ₃ PbBr ₃ ‐G composite exhibited enhanced saturable absorption properties with large modulation depth and very low saturation intensity. The transient absorption spectra and carrier dynamics analysis revealed that the enhancement of the saturated absorption properties of the composites mainly arose from the ultrafast charge transfer between G and CH ₃ NH ₃ PbBr ₃ which promoted the coupling between different states. The results pave the way for the design of optical switches or mode lockers based on saturable absorbers with good performance.

CdSe-reduced graphene oxide (CdSe/RGO) composites were synthesized by a hydrothermal method. CdSe/RGO composites with different mass ratios were prepared. The structure and morphology of CdSe/RGO composites were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The synthesis of CdSe/RGO complexes was successfully demonstrated by Fourier infrared (FT-IR) and Raman spectra. CdSe nanoparticles in the CdSe/RGO composite were uniformly dispersed on the graphene surface. The study found that oxygen-containing functional groups such as hydroxyl (-OH) and carboxyl (-COOH) groups in graphene played a decisive role in the dispersion of CdSe. The third-order nonlinear optical properties of CdSe/RGO composites were measured by a single beam Z-scan technique. The experimental results showed that composites exhibited two-photon absorption and self-focusing nonlinear refraction properties. Additionally, the third-order nonlinear susceptibility of the composite material was obviously enhanced, which was mainly due to the good dispersion of CdSe nanoparticles on graphene.

Regulating nonlinear optical (NLO) absorption and refraction properties of graphene is significant in nonlinear photonics. In this work, the functionalizing strategy of quantum dots (QDs) was used for the regulation of the NLO properties of reduced graphene oxide (rGO) with Au nanospheres and Au@CdS core-shells. The third-order NLO properties of rGO-Au and rGO-Au@CdS nanocomposites were investigated by Z-scan technique with 38 ps laser pulses at 532 nm wavelength. The saturation absorption (SA) of rGO was weakened when it was combined with Au nanospheres and switched to reverse saturation absorption (RSA) when combined with Au@CdS core-shells as irradiance intensity increased. The strength of RSA was tunable with the size of Au@CdS core-shells. Meanwhile, the nonlinear susceptibility of rGO was weakened with the complex Au but was tunable with the complex Au@CdS and realized two times enhancement. The effect of charge transfer mechanism was proposed to explain the regulated effect.

Spiral phase plate (SPP) is the widely used method in the generation of vortex beam (VB) with fixed topological charges (TCs) for specific wavelength. Although VB with large TCs can be directly generated by using the SPP with high vortex order. The fabrication of high-quality SPPs with high vortex orders usually requires complex manufacturing process and high machining accuracy. An alternative method to generate VBs with large TCs is cascaded multiple SPPs with low order. In this study, we numerically calculate the transmitted light field of cascaded multiple SPPs according to the Huygens–Fresnel diffraction integral, and perform the experimental verifications. Based on cascading 6 SPPs (3 SPPs with TCs of 2, and 3 SPPs with TCs 4, respectively), an VB with TCs as high as 18 is generated. Furthermore, The TCs of the generated VB are detected by coaxial and off-axis interfering with fundamental Gaussian beam or its conjugate beam, respectively. The generated fork and spiral patterns allow us to distinguish the value and sign of TCs carried by the VB. The experimental results coincide well with the theoretical simulations. The fork pattern shows better resolution than the spiral one, and the petal pattern with small spiral allows us to distinguish large TCs with a higher resolution.