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Two-dimensional (2D) layered materials have attracted increasing attention in recent years because of their abundant material categories and superior physical/chemical properties. In order to satisfy the requirements for highly integrated devices in the post-Moore era, substantial efforts have been devoted to producing atomically thin 2D materials with large lateral dimensions and high crystalline quality. The controllable synthesis is the precondition of the implementation of large mass producing 2D material in industry. Chemical vapor deposition (CVD) is a powerful method widely used in the synthesis of 2D materials and their hybrid structures. However, it is still challengeable to flexibly and easily grow any 2D materials into large area. Therefore, a systematic understanding of the requirements for controllable growth of different 2D materials are desired. In this review article, we provide a comprehensive discussion on the influencing factors, material transport, nucleation and growth rate in the CVD growth process. Finally, the strategies to further improve the size and quality of 2D materials are prospected.

With the advent of the post-Moore era, the demand for large-capacity and high-speed information processing has caused the application of semiconductor devices to shift from electronic integration to photonic integration. High-performance micro-nano lasers are an important part of achieving photonic integration. Varieties of semiconductor materials have promoted the rapid development of semiconductor micro-nano lasers. In recent years, with the advent of a large number of new semiconductor materials (such as two-dimensional semiconductors, lead halide perovskites, etc.), it is expected that the performances of semiconductor micro-nano lasers will be further improved. Perovskite materials have excellent optical properties such as high light absorptions, high defect tolerances, and large exciton binding energy, which make them excellent candidate materials for high-gain, low-threshold semiconductor micro-nano lasers. The Fabry-Perot (F-P) resonator laser is a type of perovskite laser with extensive research, simple structure and high application value. In this paper, we take lead halide perovskite F-P resonator laser for example, and summarize its working mechanism and recent research results, by starting from two aspects of photon laser with exciton and photon weak coupling and strong coupling polariton laser. And we introduce the lasing principle and influencing factors of F-P structure lasers with perovskite materials as both gain medium and resonant cavity and F-P cavity lasers with perovskite as only gain medium in detail. Finally, the current challenges of perovskite F-P resonant lasers are summarized, and the possible prospects of its further development are also presented.

The properties of spherical dilaton black hole spacetimes are investigated through a study of their geodesics. The closed and non-closed orbits of test particles are analysed using the effective potential and phase-plane method. The stability and types of orbits are determined in terms of the energy and angular momentum of the test particles. The conditions of the existence of circular orbits for a spherical dilaton spacetime with an arbitrary dilaton coupling constant α are obtained. The properties of the orbits and in particular the position of the innermost stable circular orbit are compared to those of the Reissner–Nordstrom spacetime. The circumferential radius of innermost stable circular orbit and the corresponding angular momentum of the test particles increase for α≠0.

The quantum nonthermal effect of the spherically symmetric and rotating dilatonic black holes is studied. A crossing of the positive and negative Dirac energy of particles occurs near dilatonic black holes. We find that the dilaton coupling parameter α affects the energy of spontaneous radiant particles. The energy of particles decreases when the coupling parameter α increases.

We have designed a spatially quantized diffractive optical element (DOE) for controlling the beam profile in a three-dimensional space with the help of the simulated annealing (SA) algorithm. In this paper, we investigate the annealing schedule and the neighbourhood which are the deterministic parameters of the process that warrant the quality of the SA algorithm. The algorithm is employed to solve the discrete stochastic optimization problem of the design of a DOE. The objective function which constrains the optimization is also studied. The computed results demonstrate that the procedure of the algorithm converges stably to an optimal solution close to the global optimum with an acceptable computing time. The results meet the design requirement well and are applicable.

In this paper, we discuss the optical geometry of the Kerr solutions and show the embedding diagram at the equator θ = π/2 for the optical space of the Kerr solution with a/M = 1. It is noticed that at the equator θ = π/2, the Gaussian curvature K for the ordinary space is negative and the for the optical space is positive.

The Ba even-parity J = 2 spectrum has been studied by using an autoionization approach. Energy levels of the Ba 6snd 1,3D2 Rydberg states have been measured and interpreted by the multichannel quantum defect theory. The results are in good agreement with the previous studies.

With the K matrix and multichannel quantum defect theory, we have studied the branching ratios of 3p3/2nd (J=1,3) autoionizing series of Mg above the 3p1/2 ion limit. The calculations are compared with the previous experimental spectra, and the unmeasured branching ratios are presented. The conclusion is that 3p3/2nd state prepared by the three-step excitation can form population inversion between the 3p1/2 and 3s1/2 ionic states.

The excitation spectra and branching ratios of ejected electrons of the Ba 6pns(J = 1) autoionizing states are measured using multistep laser excitation scheme and time-of-flight electron spectroscopy. The energy dependence of branching ratios of the Ba+ 6s state on energy is determined for the low-lying 6p1/2,3/2ns states, and compared with a previous R-matrix calculation.

Real-time, point-by-point localization of magnetic targets such as ferrous unexploded ordnance can be achieved by the cube magnetic gradiometer system designed by the Naval Surface Warfare Center. The localization method uses the Frobenius norm of the magnetic gradient tensor to calculate the location of the magnetic target. This method assumes that the potential field of the Frobenius norm of the magnetic gradient tensor is a prefect sphere. But the Frobenius norm of the magnetic gradient tensor has an asphericity parameter, and its potential field is an ellipsoid, which can cause asphericity error. Since the current localization method can be affected seriously by the asphericity error, an improved method is proposed in this paper to eliminate the asphericity error. The improved method is based on a new invariant, which does not contain asphericity parameter. The new invariant can be obtained by the combination of the Frobenius norm and eigenvalues of the magnetic gradient tensor. In detail the procedure is as follows: first, the magnetic gradient tensor of the center point of the regular hexahedron's six planes can be measured by the cube magnetic gradiometer system, then these eigenvalues can be calculated and combined according to a certain relationship to eliminate the asphericity parameter, then the new invariants of the six planes can be obtained, and the spatial gradient of the new invariant can be calculated from the six new invariants, then the localization of the magnetic target can be calculated from the spatial gradient of the new invariant. This improved method can overcome the asphericity error effectively, and it can be used for real-time, point-by-point localization and detection of unexploded ordnance. Simulation experiments show that the localization error of the improved method is much smaller than that of the original method, the average relative error can be reduced by 10.9%. The improved method can be deployed on the highly maneuverable platform. The platform motion will not be constrained, and the improved method will be made more effectively in detection and localization of the magnetic targets. Thus the improved method can be widely applied in naval mines localization, mineral exploration, ferrous resources exploration, moving magnetic target tracking, and other fields.

The ultraviolet beam at 266 nm was obtained by fourth harmonic generation of 1064 nm Nd:YAG laser radiation through a nonlinear crystal K2Al2B2O7 (KABO). The fundamental frequency of a flash-lamp pumped Nd:YAG laser was doubled in a β-Ba2B2O4 crystal to generate a second harmonic output at the wavelength of 532 nm, and then doubled again in the KABO crystal to generate the fourth harmonic output at 266 nm. The optical conversion efficiency from 532 to 266 nm was investigated for the first time, and 13% was achieved.

The acoustic radiation pressure expression of a multi-frequency sound source is obtained on the basis of the Fenlon theory. Then using the solution method of a monochromatic source harmonic wave directivity, farfield directivity of second-order approximate is obtained in the case of the dual-frequency sound source interaction. Subsequently, the effect of two-wave interaction on the farfield of first-order and second-order wave of either wave is studied and discussed when the initial radiation pressures and frequencies are different. The conclusion is that there are some different effects of sound wave interaction on the farfield directivity of a sound source, when the relative initial radiation pressure and frequency between the sound waves is changed.

A difference wave equation is obtained by discretizing a nonlinear acoustic wave equation in atmosphere in the second-order miniterm approximation based on the finite-difference time-domain method. And the pulsed infrasonic wave radiated by a linear array vertical or oblique propagation in moving inhomogeneous atmosphere is numerical simulated in the two-dimensional space, and sound pressure distribution after the different propagation times is investigated in the Wuhan(114 ∶20E, 30 ∶37N) of China and the initial time UT=29000s of summer and winter. The atmospheric inhomogeneity caused by the change of temperature and density, and the atmospheric motion caused by the presence of wind is considered by using the Msise00 and HWM93 models. The pressure difference pr obtained by subtracting no-windy pressure from the windy-pressure in above two seasons indicates that the wind has more influence on the sound field in the infrasonic propagation. The distribution waveform of pr is dependent on season because the actual acoustic velocity depends on season and propagation distance; The influence of wind on the nonlinear propagation is bigger than on the linear propagation.

A special prism coupling technique with the KBe2BO3F2 crystal is adopted to produce deep ultraviolet light including the fourth harmonic from an Nd:YAG laser, for which a conversion efficiency as high as 10% has been obtained.