Black phosphorene (BP) nanosheet, a new type of two-dimensional material with the characteristics of ultra-thin structure and ultra-fast conductivity, has achieved wide attention of researchers in basic research and technical application fields. However, the nonlinear optical (NLO) absorption of black phosphorene is not strong enough to meet the application requirements of NLO devices. Interconnecting black phosphorene with nano-materials is an effective method to improve its NLO effect. In this work, Ag nanoparticles were anchored on the surface of BP nanosheets by thermochemical method and the BP/Ag nanohybrids (NHs) were successfully formed, which is certified by TEM, XRD, Raman and XPS measurements. The covalent functionalization with Ag nanoparticles can tune the bandgap of BP nanosheets and improve their NLO response. Compared with the NLO simple addition of BP and Ag, the additional synergistic effect between them plays a major role in enhancing the NLO absorption of BP/Ag nanohybrids, and this synergistic nonlinear enhancement is closely related to the Ag concentration and the non-radiation defect density in the nanocomposites. The NLO enhancement mechanisms of extra charger transfer and local field are confirmed by femtosecond-ultrafast dynamics analysis and FDTD calculation. This work provides the new BP/Ag NH material with good optical nonlinearity and NLO mechanism discussion for potential opto-electronical applications.
The interference patterns between two vortex beams are systematically studied in experiment. Vortex beams with different topological charges (TCs) (±1, ±2, ±3) are generated by modulating the fundamental Gaussian beam with the spiral phase plate, and an improved Mach-Zehnder interferometer is built to study these different interference patterns. When two interference beams are both plane waves, off-axis interference produces fork-shaped interference patterns. The fork direction and the fork number in the fork-shaped patterns are related to the TCs and orientation relation of two vortex beams. When two LG0l vortex beams with different curvature radii interferes coaxially, the interference pattern with a spiral structure is generated, the spiral direction and spiral leaves depend on the curvature radii and TCs of two interfered vortex beams. Coaxial interference of two vortex beams with the same curvature radius produces the spiral-shaped pattern with a petal-shaped (or wheel-shaped) structure (a composite vortex field).
Black phosphorus (BP), an emerging 2D semiconductor, bridges the energy band gap between the zero-band gap graphene and large band gaptransition metal dichalcogenides owing to its size-dependent tunable band gap. In the past few years, significant progress has been made in the structure design, growth and optical properties of BP, yet studies on the size-related nonlinear optical performance need to be carried out. To investigate the correlation between size and the nonlinear optical response, we prepared BP nanosheets and quantum dots via thermochemical method, which are determined by experimental measurements of TEM characterization. The nonlinear optical absorption of BP are enhanced 16.6 times with the size decrease, which might be attributed to the photoinduced dipole moment. Tuning the size of BP nanomaterials is a useful way to enhance the optical nonlinearity for potential applications in optical and optoelectric devices
Theoretical calculations of the output characteristics about the periodically poled crystals-based intra-cavity second harmonic generation of the resonant wave in the singly resonant optical parametric oscillator (IC-SHG-SRO) are presented. Under the collimated Gaussian beam approximation, simple models are set up and the outputs of the IC-SHGSRO are shown theoretically. The calculations based on the experimental parameters are in good agreement with the experimental results. The output characteristics of the 532 nm green laser pumped IC-SHG-SRO resonating at 795 nm and the 1064 nm infrared laser pumped IC-SHG-SRO resonating at 1590 nm are predicted. The calculations demonstrate that there exists the optimum length of SHG crystal to obtain the maximum SH output for the given experimental conditions. These calculations and the models provide guidelines for designing and optimizing the continuous-wave ICSHG- SRO.
In the past few years, significant progress has been made in the structure design, growth and nonlinear optical properties of graphene and graphene-based nanohybrids. The surface defects on the nanomaterials play an important role on the optical nonlinearity of graphene and graphene-based nanohybrids owing to a large surface-to-volume ratio in the nanomaterials. To investigate the correlation between surface defects and the synergistic nonlinear optical response in graphene-based nanocomposites, we attached CdS nanocrystals on the surface of graphene and prepared G/CdS nanohybrids and graphene nanosheets consisting of different oxygen-containing functional groups via chemical method, which are determined by experimental measurements of FTIR and XPS characterization. The nonlinear optical absorption and refraction of G/CdS nanohybrids under single pulse laser irradiation are enhanced 10.8 times with the concentration decrease of surface oxygen-containing groups, which might be attributed to the local field effects and synergetic effects stemming from charge transfer between the two components. Surface oxygen-containing defects tuned nonlinear optical absorption and refraction of graphene nanosheets are also investigated. Tuning the surface oxygencontaining defects of graphene and G/CdS nanohybrids is a useful way to enhance the optical nonlinearity for potential applications in devices.
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