In this work, we demonstrate the stabilization of two-dimensional soliton families, including fundamental solitons and soliton clusters, in the nonlinear Schrödinger equation with the nonlinearity arranged as a saturable quasi-nonlinear lattice. We discover interesting properties of these families by presenting their intensity profiles, powers, amplitudes, and perturbed propagations. The most interesting finding is their improved stability, as compared to the case of a Kerr (cubic) nonlinear lattice. The radii of both fundamental solitons and soliton clusters decrease with the propagation constant, while the amplitudes increase. Curiously, the power of these solitons and clusters always increases with the propagation constant, rising sharply when the propagation constant approaches its critical value. Furthermore, the critical propagation constant decreases as the saturation parameter increases. In addition to studying the perturbed propagation of these waves, we also investigate the propagation under a dynamically modulated saturation parameter.

Due to the lack of theoretical research on the amount of spatio-temporal information in high-speed photography technologies, obtaining an optimized system with the best amount of spatio-temporal information remains a challenge, resulting in insufficient effective information and observation accuracy for ultrafast events. This paper presents an ultrafast raster imaging (URI) system with a large amount of spatio-temporal information based on the all-optical raster principle in single-shot. Specifically, we derive the optimal equation of spatial resolution and the expression for the maximum amount of spatio-temporal information that can achieve excellent performance for a URI system. It serves as a general guideline for obtaining a large amount of information design in the URI system. Compared with the existing URI systems, the advanced URI system exhibits an improvement of nearly one order of magnitude in the amount of spatio-temporal information and more than twofold in spatial resolution. It shows great potential for capturing intricate and non-repetitive ultrafast events on the femtosecond time scale.

Compared with computational imaging, direct imaging is still a concern since it provides more intuitive and reliable spatiotemporal information of the target. The paper presents a single-shot ultrafast framing direct imaging based on polarization-spatial-encoding via non-collinear optical parametric amplification (OPA) with remarkable imaging seed and spatiotemporal resolutions. Here, a 2 × 4 architecture is designed for eight optical parametric amplifiers to get eight frames by polarization splitting. This architecture effectively suppresses signal depolarization and diffraction effects, particularly mitigating nonlinear effects during pump propagation, thus enhancing imaging quality compared with a 1 × 8 design. Targeted with laser-induced air plasma, our experiments verify that the single-shot imaging system has carried out 8-frame direct imaging by 25 fs temporal resolution, 40 trillion frames per second (Tfps) effective frame rate, and beyond 25.6 lp/mm spatial resolution over a 10 × 10 mm² field-of-view. The experimental results also show the capture of richer spatiotemporal details of air plasma in the early stage (0∼3.6 ps) after excitation. The temporal window can be flexibly expanded by changing the frame interval. This work provides a powerful tool for accurately understanding dynamic processes on the femtosecond to picosecond scale for non-repeatable or random dynamic scenarios.

In many scenarios, it is really desirable but challenging for wide-field imaging to gather both the clear morphologies and fine details of the target. This paper realizes this imaging by a dual-mode imaging on optical parametric amplification (OPA) with a vortex laser pump. This design includes signal imaging and idler imaging, which have complementary point spread functions with each other. The signal acts as bright-field imaging to record morphologic information, whereas the idler does so for spiral phase contrast imaging to capture the featured details with high brightness and contrast, which has been experimentally confirmed with a target of herb tissue. By utilizing the coupling relation among the pump, signal, and idler, the information from the recorded signal and idler images can be merged, which allows us to reconstruct the target picture owning both high-contrast morphologies and high-brightness fine details. Due to high OPA gain, our imaging can work with weak illumination. Its field-of-view covers an area of 0.33 × 0.33 mm2 with a spatial resolution up to 228 lp/mm. This OPA imaging also provides an effective way for the imaging required nonlinear frequency conversion.

Due to the lack of theoretical research on the amount of spatio-temporal information in the high-speed photography technologies, obtaining an optimized system with a best amount of spatio-temporal information remains a challenge, resulting in insufficient effective information and observation accuracy for ultrafast events. The paper presents an ultrafast raster imaging (URI) system with a large amount of spatio-temporal information based on the all-optical raster principle in single-shot. Specifically, we derive the optimal equation of spatial resolution and the expression for the maximum amount of spatio-temporal information that can achieve excellent performance for an URI system. It serves as a general guideline for getting a large amount of information design in the URI system. Compared to the existing URI systems, the advanced URI system exhibits an improvement of nearly 1 order of magnitude in the amount of spatio-temporal information, and more than twofold in spatial resolution. It shows a great potential for capturing intricate and non-repetitive ultrafast events on the femtosecond time scale.

High-quality single-shot measurement for the complete characterization of ultrafast light fields remains challenging. This paper proposes SS-TSPS-SPIDER, a single-shot scheme combining spectral phase interferometry for direct electric-field reconstruction (SPIDER) with two-step phase-shifting (TSPS). This design uses a non-polarizing beam splitter to combine two orthogonally incident sum-frequency pulses, from whose two outputs it acquires two spectral interferograms with a π-phase shift. Our experimental results demonstrate that the setup can measure the group delay dispersion of a 3-mm-thick BK7 glass with an error of less than 14.1 mrad over a 45 THz range centered at 375 THz, corresponding to a 10 dB spectral bandwidth, exhibiting superior measurement accuracy and a higher signal-to-noise ratio compared with traditional SPIDER. Thus, SS-TSPS-SPIDER is well suited for characterizing ultra-intense, low-repetition-rate or single-shot ultrashort pulses, which are vital in strong-field physics, attosecond science and other extreme-physics frontiers .