[en] With the combination of CCD imaging unit and traditional multi-image camera to measure far-field distribution of laser output, the reconstruction algorithm for focal spot of high-power-solid-state laser output was described. The geometric cores of these focal spots was abstracted to center these spots by virtue of edge computational kernel applied in the field of image processing, nesting algorithm for focal spot reconstruction is put forward. It can precisely center these spots even if they are saturated partially and instantly reconstruct original focal spot, which makes it feasible to provide real-time data for laser control

[en] Highlight• A UV frequency modulation pulse waveform measurement scheme based on lens array and fiber bundle is exploited, which immensely improve the coupling efficiency coupling to fiber. Owe to the high coupling efficiency, the scheme can achieve high precise measurement result as well as good economy and anti-interference performance. • A 50μm core diameter and 0.2 numerical aperture multi-mode UV fiber is specially designed and developed. Contribution to the design of OH- and Fluorine jointly adulteration, the fiber can achieve 9.2GHz bandwidth and 32% transmittance after transmitting 60m. • A “four-in-one” measurement system based on the scheme and fiber is manufactured. In the system, four fiber bundles are used for time division multiplex and the experiment indicated that all four waveform measurement result from fiber bundles are identical to the measurement result focusing all over the near-field. • This scheme exploited has greatly improved waveform measurement precise and anti-interference performance on ICF facility, which also has great significance for ICF research. In high power laser facility, the waveform measurement of UV pulse injected to target is very important for power balanced control and experiment result analysis. A time division multiplex UV frequency modulation pulse waveform measurement system based on fiber bundle and lens array is built for a high precise measurement result as well as low construction and maintaining cost. The system can remarkably improve coupling efficiency inject to fiber contribution to the aperture splicing sampling technology and a 50μm multi-mode UV fiber specially developed with 9.2GHz bandwidth@60m transmission. A “four-in-one” time division multiplex measurement system is built for laser facility and the practical experiment indicated that the system can realize precise waveform measurement within good economy and anti-interference performance.

[en] For the measurement of single shot femtosecond laser pulse, to describe the influence of incident angle and crystal rotation on the output signal accurately, the third harmonic process is analyzed and deduced. In this article, the range of the angle of incident light is derived and calculated mathematically. At the same time, the relationship between the output autocorrelation signal and the crystal's attitude is analyzed quantitatively. The results show that, to satisfy the phase matching condition, the minimum value of the incident angle is 30.114°. The output direction of the autocorrelation signal is insensitive to the rotation of the crystal. However, the output intensity is sensitive to the intersection angle of two incident beams. The capacity of the crystal rotation is large, and the thinner the crystal is, the less sensitive it is. Moreover, the time resolution of the correlation signal is determined by the angle between the two incident beams in the crystal, the change of the angle outside the crystal does not change the time resolution. The study has reference value for the precise adjustment of femtosecond laser pulse measurements. (authors)