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• A method of CW laser-assisted splitting of SiC wafer based on modified layer by picosecond laser. • A model of modified layer under CW laser was established, the mechanism of CW laser induced SiC wafer splitting was analyzed. • The splitting of 1cm×1cm×500μm SiC wafers was achieved without applying external force with optimized laser parameters. Silicon carbide (SiC), the third-generation semiconductor material, is important in developing electronic power devices. Compared to wire sawing technology, Laser splitting SiC is an efficient way to produce SiC wafers with reduced material loss. In this work, we propose a new method of continuous wave (CW) laser-assisted splitting of SiC wafer based on modified layer by picosecond laser. For the process of CW laser irradiation on the modified layer, thermal–mechanical numerical simulations were performed to calculate the temperature and stress fields during laser loading. The mechanism of CW laser-assisted SiC wafer splitting was analyzed to guide the selection of CW laser parameters. The microstructure, element distribution, and stress state of the split SiC wafer surface were investigated and analyzed. The results showed that laser processing did not affect the crystal structure and carrier concentration of SiC. Compressive stress was generated on the splitting surface. Polycrystalline carbon and single crystalline silicon appeared on the splitting surface with a 50-250 nm thickness. The layer with compressive stress and polycrystalline microstructures can be removed after grinding and polishing. [ABSTRACT FROM AUTHOR]

• We present a broadband nanosecond superfluorescent fiber source (ns-SFS). • The impact of the active fiber' s length on the output spectrum of SFS is investigated theoretically and experimentally. • All-fiberized ns-SFS amplifier with average power of greater than 440 W, pulse energy of 17.6 mJ is achieved. In this work, we demonstrate a broadband nanosecond superfluorescent fiber source (ns-SFS) with an average power of several hundred watts and an adjustable repetition frequency of 25 kHz–100 kHz. To figure out a suitable active fiber length for ns-SFS seed, the impact of active fiber length on the output spectrum of SFS is investigated theoretically and experimentally. The results indicate an evident redshift in the central wavelength of output spectrum with increasing fiber length. By scaling the power of the ns-SFS seed employing three amplifier stages, the maximum average power and pulse energy are obtained with a value of 463 W, 17.6 mJ, respectively. To the best of our knowledge, this work is the first demonstration of a broadband ns-SFS amplifier with output power exceeding hundred watt and pulse energy exceeding 10 mJ. [ABSTRACT FROM AUTHOR]

• A simplified model of laser cleaning plume ejection angle was established, and the plume ejection characteristics were observed by high-speed camera. The calculation results are in agreement with the experimental results. • The laser cleaning process parameters were optimized to realize the laser cleaning of ferrite paint without spatter on the surface. • It is found that the iron in ferrite may be reduced during the laser paint removal process, which may affect the wave absorption of the paint. Ferrite paint are commonly used on the surface of aluminum alloys. It contains metal oxide particles, significantly affecting laser paint removal when a nanosecond pulsed laser was used to clean the ferrite paint. In this paper, we experimentally investigate and analyze the plume ejection characteristics and the product during the laser cleaning of the paint. Driven by ablative gas recoil pressure, the ferrite paint was vaporized by the laser pulse into a mixture of molten droplets, resin residual particles, and carbides, and they were then ejected from the laser scanning area with the plume to form a black spatter powder on the cleaned surface. A physical model for calculating the ejection angle of the laser-cleaning plume is established. The results show that the thermal diffusion rate of paint and substrate, laser pulse duration, and laser scanning speed determine the plume ejection angle. Optimizing laser defocus distance and lap rate could significantly reduce surface spatter and improve cleaning quality. Furthermore, through the analysis of XPS, we found that the valence state of the residual ferrite paint changes after the laser cleaning and may affect the residual paint's microwave-absorbing performance. Therefore, removing the ferrite paint layer completely and then re-spray rather than only removing a certain paint depth is necessary. [ABSTRACT FROM AUTHOR]

• Based on the principle of complete randomness of digital chaos equation, a 3D imaging LIDAR system is established, which can automatically eliminate the ranging ambiguity and realize the imaging of high repetition frequency pulse larger than 1 MHz. • A slope distribution characteristics algorithm has been proposed, can be in a chaotic degree higher point cloud image with continuous feature points are extracted accurately, so as to realize the precise imaging. • Under the periodic interference sources and random interference sources of the disturbance, the system still has more than 98.79% of the imaging accuracy. Pulsed imaging light detection and ranging (LIDAR) based on time-of-flight (ToF) ranging has developed rapidly. However, due to the inherent periodicity of laser pulses, ranging ambiguity and interference from other laser pulses would seriously degrade the accuracy of imaging. In this paper, a set of 3D imaging LIDAR model was established and its imaging characteristics were numerically simulated. Based on the principle of complete randomness in terms of the digital chaos equation, the pulse position modulation of light source can be realized. By comparing pulse ranging distance characteristics before and after the modulation, this paper proposed a slope distribution characteristic algorithm. Combining with this algorithm, we successfully eliminated the ranging ambiguity, and reduced the deviation between the actual distance and the calculated distance down to 0.52%. At the same time, we have studied the anti-interference performance of the proposed model. Under the interference of 1 MHz periodically pulsed laser, combined with the algorithm, the correct point clouds are obtained, and the average distance deviation from the point clouds without interference is about 0.56%. The average distance deviation of point cloud image before and after random pulse interference is about 1.21%. [ABSTRACT FROM AUTHOR]