In this paper, we review the status of the multifunctional experimental platform at the National Laboratory of High Power Laser and Physics (NLHPLP). The platform, including the SG-II laser facility, SG-II 9th beam, SG-II upgrade (SG-II UP) facility, and SG-II 5 PW facility, is operational and available for interested scientists studying inertial confinement fusion (ICF) and a broad range of high-energy-density physics. These facilities can provide important experimental capabilities by combining different pulse widths of nanosecond, picosecond, and femtosecond scales. In addition, the SG-II UP facility, consisting of a single petawatt system and an eight-beam nanosecond system, is introduced including several laser technologies that have been developed to ensure the performance of the facility. Recent developments of the SG-II 5 PW facility are also presented.

A single shot multi-wavelength phase retrieval method is proposed by combining common coherent modulation imaging (CMI) and a low rank mixed-state algorithm together. A radiation beam consisting of multi-wavelength is illuminated on the sample to be observed, and the exiting field is incident on a random phase plate to form speckle patterns, which is the incoherent superposition of diffraction patterns of each wavelength. The exiting complex amplitude of the sample including both the modulus and phase of each wavelength can be reconstructed simultaneously from the recorded diffraction intensity using a low rank mixed-state algorithm. The feasibility of this proposed method was verified with visible light experimentally. This proposed method not only makes CMI realizable with partially coherent illumination but also can extend its application to various traditionally unrelated fields, where several wavelengths should be considered simultaneously.

An optical setup and corresponding reconstruction algorithm are proposed to realize single-shot Fourier ptychography (FP). Multiple angle-varied object waves are generated by placing a Dammann grating at a certain distance behind the object, and the generated image array of low resolution corresponding to different diffraction orders formed on the detector plane is recorded simultaneously in a single exposure. The amplitude, as well as the phase information of the object, can be properly reconstructed with a common FP algorithm from the recorded image array. This method eliminates the requirement for the angular scanning of common FP, and the total acquisition time is dramatically reduced. The feasibility of this proposed method was demonstrated both numerically and experimentally. The proposed method has the advantages of fast data acquisition and corresponding high temporal resolution, making it very suitable for applications in which high imaging speed is required.

Ultrafast imaging can capture the dynamic scenes with a nanosecond and even femtosecond temporal resolution. Complementarily, phase imaging can provide the morphology, refractive index, or thickness information that intensity imaging cannot represent. Therefore, it is important to realize the simultaneous ultrafast intensity and phase imaging for achieving as much information as possible in the detection of ultrafast dynamic scenes. Here, we report a single-shot intensity- and phase-sensitive compressive sensing-based coherent modulation ultrafast imaging technique, shortened as CS-CMUI, which integrates coherent modulation imaging, compressive imaging, and streak imaging. We theoretically demonstrate through numerical simulations that CS-CMUI can obtain both the intensity and phase information of the dynamic scenes with ultrahigh fidelity. Furthermore, we experimentally build a CS-CMUI system and successfully measure the intensity and phase evolution of a multimode $Q$-switched laser pulse and the dynamical behavior of laser ablation on an indium tin oxide thin film. It is anticipated that CS-CMUI enables a profound comprehension of ultrafast phenomena and promotes the advancement of various practical applications, which will have substantial impact on fundamental and applied sciences.

We present the design and experiment of a broadband optical parametric chirped-pulse amplifier (OPCPA) which provides high conversion efficiency and good beam quality at 808 nm wavelength. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good beam quality and good output stability are discussed. To improve the conversion efficiency and broaden the amplified signal bandwidth simultaneously, the nonlinear crystal length and OPCPA parameters are analyzed and optimized with the concept of dissipating amplified idler between optical parametric amplification (OPA) of two crystals configuration. In the experiment, an amplifier consisting of two OPCPA stages of ‘L’ type configuration was demonstrated by using the optimized parameters. An amplified signal energy of 160 mJ was achieved with a total pump-to-signal efficiency of 35% (43% efficiency for the OPCPA stage 2). The output bandwidth of signal pulse reached 80 nm and the signal pulse was compressed to 24 fs. The energy stability reached 1.67% RMS at 3% pump energy variation. The optimized OPCPA amplifier operates at a repetition rate of 1 Hz and is used as a front-end injection for the main amplifier of SG-II 5PW laser facility.

Aperture-scanning Fourier ptychography [Opt. Express 22, 13586 (2014)] is a promising non-interferometric wavefront measurement technique. It eliminates the thin-sample requirement in typical Fourier ptychography employing angle-varying illumination. However, as aperture-scanning Fourier ptychography is based on step-by-step scanning, it requires long data acquisition time and a high-stability optical system. In this paper, we propose a single-shot aperture-scanning Fourier ptychography method. In our method, multiple low-resolution images are collected in a single shot by inserting a Dammann grating at a certain distance before the aperture, and the images are subsequently converted to a high-resolution complex wavefront. Compared with scanning-based aperture-scanning Fourier ptychography, the total acquisition time of the proposed method is dramatically reduced. The feasibility of our proposed method is demonstrated by proof-of-concept experiments.