Mid-infrared (MIR) lasers have various advantages and can be widely used in either fundamental research fields or practical applications such as strong-field physics, molecular sensing and minimally-invasive tissue ablation. Generally, there are two categories of methods to generate MIR laser emission: one is direct lasing and the other is nonlinear frequency down-conversion. However, for the ultra-broadband few-cycle MIR generation, nonlinear down-conversion is the only available method. Intra-pulse Difference Frequency Generation (IP-DFG) is a simple method of nonlinear frequency conversion. In this article, the IP-DFG technology for the ultra-broadband MIR few-cycle pulses generation is reviewed. Different MIR nonlinear crystals, various driving laser sources, the spectral coverage of the MIR-IPDF output, and the conversion efficiency are compared and discussed. Last but not least, the prospects and challenges of MIR IP-DFG are presented.

In recent years, Adaptive Optics (AO) system is developing towards miniaturization and low cost. Because of its simple structure and wide application range, wavefront sensorless (WFSless) AO system has become a research hotspot in related fields. Under the condition that the hardware environment is determined, the system control algorithm determines the correction effect and convergence speed of WFSless AO system. The emerging deep learning and artificial neural network have injected new vitality into the control algorithms of WFSless AO system, and further promoted the theoretical and practical development of WFSless AO. On the basis of summarizing the previous control algorithms of WFSless AO system, the applications of convolution neural network (CNN), long-term memory neural network (LSTM) and deep reinforcement learning in WFSless AO system control in recent years are comprehensively introduced, and characteristics of various deep learning models in WFSless AO system are summarized. Applications of WFSless AO system in astronomical observation, microscopy, ophthalmoscopy, laser telecommunication and other fields are outlined.

Beam scanning technology based on optical phased arrays has great potential for applications in the fields of LIDAR, space optical communication, and optical switching. Among them, the microlens array optical phased array can modulate the tilted phase of multiple beams simultaneously through the relative displacement of micrometer scale between microlens arrays, so as to achieve large angle beam scanning, with the advantages of large emitting aperture, simple structure, small size, micro-inertia, etc. Several well-known institutions at home and abroad have conducted research on the microlens array optical phased array. This paper first introduces the scanning principle of microlens array optical phased array, then elaborates on its development status and application, and finally gives an outlook on the trend of its development.

Power supply prototype in High Intensity heavy ion Accelerator Facility-Booster Ring (HIAF-BRing) adopts the scheme of full energy and fast cycle storage pulse power supply topology. Its multi modules are connected in series and parallel pattern, and the power reaches megawatt level. Due to the high power and large scale of the power supply, a module fault interlock protection system based on Programmable Logic Controller (PLC), interlock boards and Field Programmable Gate Array (FPGA) is designed and implemented to protect the power supply in operation. In this paper, first, a design of double redundant module fault interlock is introduced. Second, the logic implemented in PLC is described. Third, the work about FPGA is given. Finally, the system is tested in three aspects: the responsive time of the power supply interlock loop, the total time from controller error occurrence to interlock finish, and the equipment fault response. The result shows that the module fault interlock system can action sensitively, timely and reliably in case of fault occurrence, which meets the requirements of the power supply prototype in HIAF-BRing.

High purity graphite with purity above 99.9%, as an industrial raw material, plays an important role in the high-tech field. The existing physical and chemical methods of graphite purification technology has high cost serious damage to equipment and environment by acid and alkali, and complex processes. Thus the development of an excellent and effective graphite purification technology has become a research hotspot in recent years at home and abroad. A purification method of flaky graphite by arc plasma is established in this paper. The characteristics of high temperature which can be produced quickly by using arc plasma is used to treat the flaky graphite samples with a purity of 94.18% from Jixi City of Heilongjiang Province, under high temperature. The results show that the optimal discharge parameters are air flow rate 25 L/min, current 400 A and power 10 kW. At this point, the surface temperature of the arc plasma is up to 3350 ℃. Scanning electron microscope is used to compare the microstructure of graphite samples before and after arc processing to find the characteristics of shredding and breaking of graphite samples. The graphite purity and impurities are analysed according to national standard chemical analysis method of GB/T 3521 2008. After arc treatment, the purity of graphite is increased to 99.21%.

An all-solid-state LC-Marx generator based on magnetic switch has been proposed and analyzed by theory, simulation and experiment. This system is controlled by 1 MOSFET and magnetic switches that are made by 1 magnetic core. It has dimensions of 130 mm (diameter) and 60 mm (height), which almost not change with the stage increase. The capacitors could be charged to 1.82 times source voltage according to the principle of resonant charging. Five-stage LC-Marx generator could obtain a peak output voltage of −10.9 kV with rise time of 80 ns when the source voltage of 950 V is applied, and the energy efficiency is 30.43% on 500 Ω. The generator has been tested under 30 kHz that could work steadily. It could output higher voltage when used for atmospheric discharge.

Based on thermal stability and vibration stability, an ultra stability structure of rigid support is designed and optimized. Through the finite element modal analysis of ANSYS, the thermal expansion variation and the characteristic frequency of the support is verified. The support is fixated to the ground by using the method of concrete grouting and then the characteristic frequency is tested. The test results show that the characteristic frequency of the support reaches up to 61.9 Hz and the vibration amplitude is less than 30 nm, both of which meet the design requirements. Finally, the method of dynamic stiffness testing is adopted to obtain the stiffness value of the concrete grouting, and the accuracy of the optimization results of the support is further verified.

The effect of plasma on the transmission properties of electromagnetic waves and its application have always been one of the key research directions of electromagnetic theory and technology and plasma physics. The enhancement effect of collisional plasma on electromagnetic waves is a classic subject of the interaction between electromagnetic waves and plasma. Based on the transmission characteristics of electromagnetic waves in medium, this paper takes plasma as a special medium, and carries out experimental, theoretical and simulation studies on the transmission characteristics of high power microwave (HPM) atmospheric plasma and a certain range of electromagnetic waves under certain experimental conditions. The study found that the plasma formed by the S-band HPM under a vacuum of 50 Pa has a great influence on the electromagnetic wave transmission characteristics of different frequencies, and the electromagnetic wave transmission signal enhancement effect occurs regularly within a certain frequency range. A series of transmission waveforms of continuous electromagnetic waves of different frequencies passing through the HPM plasma area were obtained, and the waveforms were normalized. At 32.4 GHz, the transmission coefficient of continuous electromagnetic waves passing through the plasma area with plasma is about twice as high as that through the area without plasma. A simulation model was established, and the transmission coefficient distribution curve in the range of 31.5−32.5 GHz was obtained. The electromagnetic wave passing through the plasma showed a transmission enhancement effect, and at some frequency points, there was a transmission enhancement of about 1.9 times. The research results provides important technical support for the application of plasma in stealth, emergency communications, and black barrier communications.

The report about mode instability in 2010 has begun the history of struggling with the waste heat in fiber lasers. This paper presents a 10-year research progress of mode instability research, including physical demonstrations, physical mechanism, theoretical investigation, various impact factors and effective mitigating strategies. The most recent results on mode instability suppressing are also included as well as the future development trend of mode instability research.

Laser fusion, likely the ultimate solution to the crisis of human energy, is highly valued by the international community and has always been the focus of international research. It turns out that the biggest scientific obstacle of laser fusion is the effective control of the high-energy-density nonlinear flows during implosions. The research of high-energy-density nonlinear flows covers many different fields, such as high-energy-density physics, plasma physics, fluid mechanics, computing science, strong impact physics, and high pressure atomic physics. Meanwhile, the capability of multi-material and multi-scale numerical simulations as well as large laser facility with high output power is also needed. As an emerging research field, it is full of all kinds of novel phenomena to be explored. In addition, hydrodynamic instabilities and the subsequent turbulent mixing in high-energy-density flows, are also important processes in astrophysical phenomena (e.g., galaxy collision and merging, stellar evolution, formation of protostars and supernova explosion) and involve with the core content of astrophysics. This paper reviews, firstly the status and progress, as well as the challenges and opportunities of high-energy-density nonlinear flows research. Secondly, it introduces hydrodynamic instabilities during implosions in central ignition laser fusion, among which, key factors related to the bottleneck of implosion performance of the National Ignition Facility (NIF) in the United States are condensed. Next, it summarizes the development of hydrodynamic instability experiments in laser fusion abroad. Finally, it lists some key achievements on the fundamental issues of hydrodynamic instabilities by the laser fusion implosion physics team in China over the last three years. This team has been engaged in the research and control of nonlinear flows in laser fusion implosions, as well as the research and design of target physics. A lot of improvements have been made in recent years on the theoretical analysis and numerical simulation of outstanding issues for hydrodynamic instabilities in laser fusion implosions, and the design and analysis of experiments on large lasers, which greatly promoted the development of this research direction in China.