Auto-alignment is a basic technique for high-power laser systems. Special techniques have been developed for laser systems because of their differing structures. This paper describes a new sensor for auto-alignment in a laser system, which can also serve as a reference in certain applications. The authors prove that all of the beam transfer information (position and pointing) can theoretically be monitored and recorded by the sensor. Furthermore, auto-alignment with a single lens sensor is demonstrated on a simple beam line, and the results indicate that effective auto-alignment is achieved.

Light carrying orbital angular momentum (OAM) has a spatial distribution of intensity and phase, which attracts considerable interest regarding several potential applications in optical and quantum scenarios recently. Spiral phase plates are commonly used elements for generating and analyzing OAM states. In this study, we put forward a method of directly writing binary multi-sector phase plates using the femtosecond laser. These phase plates are engraved on fused silica, which could be applied in high-intensity regimes. Different binary multi-sector phase plates were generated with high quality, which were proved by the observation of their structures, accompanied by detecting the beam patterns with the Gaussian beams. The proposed method provides a crucial basis for the rapid manufacturing of phase plates using convenient equipment, which can generate the superposition OAM states and may lead to the capability of measuring the high-dimensional entanglement.

Temporal contrast is one of the crucial physical determinants which guarantee the successful performance of laser–matter interaction experiments. We generally reviewed the influences on the temporal contrast in three categories of noises based on the requirement by the physical mechanisms. The spatiotemporal influences on temporal contrast at the focal region of the chromatic aberration and propagation time difference introduced by large-aperture broadband spatial filters, which were spatiotemporally coupled with compression and focusing, were calculated and discussed with a practical case in SG-II 5 PW ultrashort petawatt laser. The system-wide spatiotemporal coupling existing in large-aperture broadband ultrashort petawatt lasers was proved to be one of the possible causes of temporal contrast degradation in the focal region.

The Shen-Guang II Upgrade (SG-II-U) laser facility consists of eight high-power nanosecond laser beams and one short-pulse picosecond petawatt laser. It is designed for the study of inertial confinement fusion (ICF), especially for conducting fast ignition (FI) research in China and other basic science experiments. To perform FI successfully with hohlraum targets containing a golden cone, the long-pulse beam and cylindrical hohlraum as well as the short-pulse beam and cone target alignment must satisfy tight specifications (30 and $20~\unicode[STIX]{x03BC}\text{m}$ rms for each case). To explore new ICF ignition targets with six laser entrance holes (LEHs), a rotation sensor was adapted to meet the requirements of a three-dimensional target and correct beam alignment. In this paper, the strategy for aligning the nanosecond beam based on target alignment sensor (TAS) is introduced and improved to meet requirements of the picosecond lasers and the new six LEHs hohlraum targets in the SG-II-U facility. The expected performance of the alignment system is presented, and the alignment error is also discussed.

Achieving ignition of ICF (inertial confinement fusion) has been the great dream that scientists all over the world pursue. As a grand challenge, this aim requires energetic and high quality lasers. High power laser facilities, for this purpose, have therefore flourished over the past several decades. Meanwhile high power laser facilities, also essential for high-energy-density (HED) scientific research and astrophysics, drive rapid progress of material science, electronics, precision machinery and so on. Many countries have successfully established a succession of facilities to study ICF and HED physics, such as National Ignition Facility (NIF)[1] in the United States and the Laser Megajoule (LMJ) in France[2]. China, conducted such research activities early, as one of the few countries having the capability of developing high power facilities independently. As the major pioneer dedicated to high power laser technology and ICF research in China, the National Laboratory on High Power Laser and Physics (NLHPLP) and its precursor have established a succession of facilities since 1973. In 1986 NLHPLP was formally established at Shanghai Institute of Optics and Fine Mechanics; this opened up a new era of laser fusion research in China. Since then the facilities at NLHPLP entered into ‘Shen Guang’ families. Since the SG-I facility dismantled in 1994, NLHPLP has successively constructed SG-II laser facility, SG-II 9th beam, SG-II upgrade (SG-II UP) facility, and SG-II 5PW facility. These operational facilities constitute a multifunctional experimental platform, which provide important experimental capabilities by combining different pulse widths of nanosecond, picosecond and femtosecond scales. SG-II facility, greatly promoting Chinese ICF research, has had a stable and excellent operation for approximately 20 years. A newly built SG-II UP facility, consisting of a single petawatt picosecond system with kJ-class output and eight-beam nanosecond capability with multi-pass amplifier configuration, has achieved the required outputs. This facility marks a major step of increasing capability of designing and constructing high power facilities. In addition, SG-II 5 PW facility is already operational for physical experiments. Construction of these facilities has driven the fabrication and processing of large optical components. Furthermore, many advanced technologies have been developed that ensured good performance of these systems. Apparently with operations spanning 30 years, NLHPLP is an important scientific research base on high power laser scientific research in China.

Optical damages, which severely degrade the output energy performance of Nd:glass regenerative amplifiers, are discussed in detail in this paper. By a series of experiments, it has been confirmed that these damages result from laser-induced contamination. Based on this work, several improvements are made to boost output energy performance of the regenerative amplifier. The output energy of the regenerative amplifier after improvements declines 4% after 1000 h of operation, much less than it used to, 60% after 560 h of operation.

A type of $\unicode[STIX]{x1D706}/4$–$\unicode[STIX]{x1D706}/4$ ultra-broadband antireflective coating has been developed using modified low refractive silica and high refractive silica layers by a sol–gel dip coating method for amplifier blast shields of the Shen Guang II high power laser facility (SG-II facility). Deposition of the first layer (high refractive index silica) involves baking at $200\,^{\circ }\text{C}$ in the post-treatment step. The second layer (low refractive index, $n=1.20$) uses low refractive index silica sol modified by acid catalysis. Thermal baking at temperatures no less than $500\,^{\circ }\text{C}$ for 60 min offers chemical stability, ethanol scratch resistance, and resistance to washing with water. The average residual reflection of dual-side-coated fused silica glass was less than 1% in the spectral range from 450 to 950 nm. Transmission gain has been evaluated by taking into account angular light, and the results show that the transmission gain increases with increasing light incidence. Even at $60^{\circ }$, the transmission spectrum of the broadband antireflective coating effectively covered the main absorption peak of Nd:glass.

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.