Stimulated Brillouin scattering (SBS) based on liquid medium is widely used in high-power laser systems, for its large-energy load, high-energy conversion efficiency, high-efficiency compression of nanosecond pulses, phase conjugation, improvement of beam quality and high quantum conversion efficiency, and so on. Liquid SBS phase conjugation, pulse compression and laser beam combination as important research directions, have received extensive attention and research of scholars all around the world. The basic principles and the properties of SBS gain media are introduced. The research progress of liquid SBS phase conjugate mirrors, pulse compressors and laser beam combination in high-power laser systems are reviewed, and the development direction is prospected.

Alexandrite is broadband tunable laser crystal with emission spectra covering 700~900 nm. Thus it also has great potential for ultrafast laser pulse generation, which has been extensively studied in recent years. At first, the structure, physical and optical properties of Alexandrite crystal are introduced. And then, the current development status in the field of ultrafast lasers is reviewed. At last, the future development is forecasted.

The difficulties to countering terminal sensitive projectile are analyzed with the attacking process characteristics and sensitive detection principle of the typical terminal sensitive projectile in foreign countries. Results show that regional active jamming is difficult to effect for the extremely close detection distance and the smaller field of view of the terminal sensitive projectile. A single countermeasure method is failure for the high hit accuracy, which uses many kinds of sensitive means of detection. The terminal sensitive projectile has characteristic of "destroy when found", motor alone can′t escape. For the efficient charge ratio, protection cost is higher. And the development idea of terminal sensitive projectile countermeasure technology is briefly introduced.

With the wide application of various new radar system technologies in the military, the future battlefield electromagnetic environment is more complex and difficult to predict. The survival environment of aircraft platform is relatively bad. Therefore, in order to cope with the threats of air defense radar, guidance radar and terminal guidance radar seeker, and effectively enhance the self-defense and penetration attack ability of aircraft platform, active decoy is paid more and more attention by all parties. The development status of various types of active radar decoys in foreign countries is introduced. The main operational strategies of active radar decoys are analyzed. And the future development trend of active radar decoys is forecasted.

According to the international standard of laser beam quality, the beam quality of coherent array laser is evaluated by the beam quality factor [M2]. And the [M2] of coherent array laser is calculated by fitting the hyperbolic equation of coherent array laser transmission under different wavelength, sub-source radius, duty cycle and array width. Considering that there is a large error in calculating the [M2] factor by fitting hyperbolic equation, the beam quality of coherent array laser is calculated by using power ratio in bucket (BQ). According to the relationship between BQ and [M2], the stable [M2] of coherent array laser under different parameters can be obtained by calculating BQ. The calculated results show that the beam quality of coherent array laser is close to the diffraction limit.

A new type of hybrid structure hollow-core polarization-maintaining fiber with high polarization-maintaining, low loss and excellent bending characteristics in the near-infrared band is proposed. The innovative hybrid structure is formed by adding a double-layer anti-resonance arc-shaped thin-wall in the core of the 19 cell photonic bandgap (PB) hollow-core fiber. On the premise of maintaining the excellent bending characteristics of the PB hollow-core fiber, the birefringence is enhanced by reducing the symmetry of the anti-resonance (AR) effect. The results of numerical simulation show that the maximum birefringence is 1.36×10-3 at the wavelength of 1 550 nm, and the corresponding confinement losses of the two fundamental modes are 1.24×10-5 dB/km and 4.64×10-4 dB/km, respectively. When the fiber is bent to a bending radius of 5 mm, the confinement loss of the two polarization fundamental modes can be less than 10-2 dB/km. The analysis of fabrication robustness shows that the PB-AR hybrid structure fiber has good transmission and polarization-maintaining characteristics even when the curvature of the arc-shaped thin-wall is changed in a small range. The PB-AR hybrid structure will provide a new impetus for structural innovation and exploration of hollow-core fiber with high polarization-maintaining and low loss characteristics under small bending radius. The excellent performance of the hybrid structure fiber will also promote the application of the hollow-core polarization-maintaining fiber.

Two mode selection methods are studied for 7-core large mode field fiber. One is the traditional Talbot cavity mode selection, and the other is the micro core diameter mode selection. Taking seven core fiber as an example, the mode selection mode of traditional Talbot cavity is theoretically analyzed and simulated, and the coupling factors between each super-mode and other modes in multi-core fiber is analyzed. In addition, a new mode selection mechanism is analyzed, that is, micro core diameter fiber is used for mode selection. Compared with the traditional Talbot cavity, it is proved that the mode selection mechanism of micro core diameter fiber is more convenient and simple to select the in-phase super-mode in multi-core fiber, which has great potential in practical application.

A fast target motion compensation method for airborne platform is proposed to solve the problem that the target position changes greatly and can’t be accurately located in the image under the condition of large maneuvering motion of the carrier. Firstly, the local area image of the target location in the previous frame is selected as the template image. Secondly, according to the position of the target in the previous frame, the detector installation angle and the aircraft attitude information, the position of the target in the current frame is predicted, and the local area image of the predicted target location as the image to be registered is obtained. Finally SIFT algorithm is applied to calculate the key points in the template image and the registered image, and accurate target position in the current frame is obtained through image registration, which ensures the accuracy of target location calculation in the image sequences. Experimental results show that the proposed method can accurately locate the position of the target in continuous frame under the condition of large maneuver flight, compared with calculating the target position through the whole image registration, the calculation efficiency is greatly improved.

When the general capacitance touch chip is used in the environment with large temperature difference range and complex electromagnetic environment, there will be the problem of false alarm point, and the number of pins is fixed and the flexibility is poor. Field programmable gate array (FPGA) is adopted as a controller, cooperating with the peripheral excitation and acquisition circuit, and combing the FPGA processing algorithm to realize the control design of the projection mutual capacitance touch screen. Through testing and verification, all indexes meet application requirements.

In order to study a new method of image denoising, the auto-encoder module in machine learning is used to optimize the image. By adding noise to the original clarity image, being taken as the input data of the auto-encoder module, and the original image without adding noise as a standard value, the auto-encoder module is trained to improve image denoising ability. Experimental results show that the auto-encoder module has a certain image denoising function after training.

An infrared spectrum data analysis method is proposed to process the original data generated by SR5000N spectral radiometer conveniently and quickly and obtain infrared radiant characteristics of infrared flare. The method has main functions of calibration, background reduction, spectrum integral, energy integral, energy ratio analysis, three dimension visualization and radiant energy calculation.

The optic-electronic countermeasure environment on the battlefield of loitering missile is analyzed. And the scenarios of laser, smoke screen, camouflage barrier and false target countermeasure in loitering missile testing are described. From the construction requirements of the optic-electronic countermeasure environment of loitering missile testing in actual combat evaluation, the key points of constructing the equipments required by these testing scenarios are analyzed systematically. It provides important references for optic-electronic countermeasure environment construction of loitering missile evaluation in the actual combat.