Researchers from SG II facility has made progress in measuring the Power Spectral Density (PSD) of large-gradient wavefronts. The team proposed a wavefront detection method based on knife-edge scanning filtering, which enables precise detection of mid-to-high spatial frequency errors in wavefronts with large gradients.

The research team from SG II facility established a 3D spatiotemporal multi-mode model for multimode lasers, and conducted an in-depth study of the spatiotemporal interactions among these modes. This work enables a quantitative description of the spatiotemporal evolution at any spatial position and temporal slice during light field propagation.

At the Shenguang-II Facility, researchers have innovatively developed an arbitrary temporal pulse shaping technique utilizing optical waveguide four-wave mixing for high-resolution laser pulse control.

Recently, a joint research team from the High Power Laser Physics Joint Laboratory at the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, collaborating with a team from Harbin Institute of Technology, has achieved anisotropic three-dimensional array beam splitting control at extremely short wavelengths.

The research team innovatively proposed and experimentally validated a nanosecond-scale pulse contrast measurement method based on laser filamentation in water. This technique utilizes nonlinear optical attenuation generated by the laser-matter interaction to effectively protect the photodiode, achieving up to 40-fold attenuation of the main pulse without affecting low-intensity prepulses.

Regarding to the precise measurement and control of time synchronization and carrier-envelope phase difference (ΔCEP) between pulses, a concise optical method based on the phase retrieval of spectral interference and quadratic function symmetry axis was proposed, which could fit to simultaneously measure the time synchronization and ΔCEP between few-cycle pulses. The control precision of our coherent beam combining system can achieve a time delay stability within 42 as and ΔCEP measurement precision of 40 mrad, enabling a maximum combining efficiency of 98.5%. This method can effectively improve the performance and stability of coherent beam combining systems for few-cycle lasers, which will facilitate the obtaining of high-quality few-cycle lasers with high energy.

Researchers from the Shenguang II team at the Joint Laboratory for High Power Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, have developed a novel machine learning-based technique for crystal self-alignment in high-power laser facilities. This method can automatically search for and align the crystal's reflected spot in approximately 10 minutes, significantly enhancing alignment efficiency.

The team discovered a novel phenomenon of dual-peak hot images induced by the cascade effect of nonlinear frequency conversion and self-focusing. Significantly, they uncovered a new principle where beam wavelength conversion causes a rearward shift of the hot image location.

A progress in wavefront Power Spectral Density (PSD) measurement based on knife-edge scanning was proposed. The team used a knife-edge lateral scanning method for wavefront detection, which could be a more efficient and automated measurement of the PSD of large-aperture optical components..

Computational optical field measurement for high-power lasers enables the simultaneous measurement of the laser's complex amplitude (intensity and wavefront/phase). It can also reconstruct the high dynamic range focal spot distributions at different planes in the far field. A new progress was proposed by integrated the measurement optical path parameters of existing setups and direct-imaging data of sampled large-aperture laser beams into the computational wavefront-coded imaging process. And also improved algorithms to effectively enhance the SNR for reconstructing the complex amplitude of large-aperture laser beams, in order to be more precious.