Due to the absence of matching carbon atoms at honeycomb centers with carbon atoms in adjacent graphene sheets, theorists predicted that a sliding process is needed to form AA, $A{B}^{\prime }$, or ABC stacking when directly converting graphite into $s{p}^3$ bonded diamond. Here, using twisted bilayer graphene, which naturally provides AA and $A{B}^{\prime }$ stacking configurations, we report the ultrafast formation of a transient two-dimensional diamondlike structure (which is not observed in aligned graphene) under femtosecond laser irradiation. This photoinduced phase transition is evidenced by the appearance of bond lengths of 1.94 and 3.14 Å in the time-dependent differential pair distribution function using MeV ultrafast electron diffraction. Molecular dynamics and first-principles calculation indicate that $s{p}^3$ bonds nucleate at AA and $A{B}^{\prime }$ stacked areas in a moiré pattern. This work sheds light on the direct graphite-to-diamond transformation mechanism, which has not been fully understood for more than 60 years.

Streak tube imaging lidar (STIL) can obtain 4-D images of a target, and its performance is mainly determined by the streak tube sensor. To obtain a large field of view, we developed a streak tube with a photocathode length as large as 35.3 mm, which is larger than the commonly used ST-HDR (30 mm). At the same time, the temporal resolution and dynamic spatial resolution are 60 ps and 12 lp/mm, which are very suitable to obtain accurate target coordinates for 4-D imaging. In addition, the streak tube has a high detection sensitivity of 46 mA/W at 500 nm and, hence, prospects in remote imaging. To test the performance of the streak tube, an underwater STIL experiment was conducted. Echo signal processing was performed by means of a bandpass filter and a matched filter, and then the peak detection algorithm was used to reconstruct the image. The results indicate that a spatial resolution better than 9 mm is achieved in the limpid water with a depth of 20 m, and a range accuracy of 1 cm is achieved in the turbid water with a depth of 10 m. Such a performance suggests that the large-field streak tube is of great potential for underwater target imaging and other remote imaging applications.

High resolution and high sensitive low light level imaging sensors are crucial in many applications such as astronomical observation, high energy physics, night vision and remote sensing. The electron bombarded complementary metal oxide semiconductor (EBCMOS) sensor is a novel imager in which very high gain can be produced by hitting the semiconductor with high voltage without any noise generation. In addition, it can process high-definition image with kHz frame rate. These advatages make the EBCMOS an ideal device for ultrafast single-photon imgaing. In this article, we present an EBCMOS sensor working in the ultraviolet range by combing the technology of vacuum photocathode and back illuminated CMOS together. This EBCMOS sensor can realize very high resolution in 40 mlx light illumination environment. The achieved spatial resolution is 25 lp/mm (line paris per millimeter) when the electric field intensity is 5000 V/mm. The liner relation between electric field intensity and the resolution indicates that much better perofromance can be achieved if the electric field intensity increases to a much higher value. The EBCMOS sensor developed in this paper can be directly applied to UV weak light detection, moreover it will provide a good reference for further developing the visible and near infrared sensitive EBCMOS sensors.

Ge/Si single- photon avalanche diodes (SPADs) plays a pivotal role in advancing silicon-based optoelectronics by enabling high-sensitivity photodetection at short-wave infrared wavelengths, a critical region for applications such as quantum communication, Light Detection and Ranging (LiDAR), and biological imaging. This review provides a comprehensive overview of Ge/Si SPAD, analyzing the fundamental principles, key performance factors, and optimization methods, including material growth, interface engineering, and structural design. We detail the evolution of major Ge/Si SPAD structures: the initial mesa type with simple design; the planar type, which enhances performance through precise doping; and the lateral type, which simplifies fabrication and innovatively combines vertical absorption with horizontal multiplication. These advancements have driven Ge/Si SPAD toward higher single-photon detection efficiency (SPDE), lower dark count rate (DCR), broader operational wavelengths, and high performance room-temperature operation. Ongoing structural optimizations not only expand design options but also contribute significantly to the advancement of silicon-based optoelectronics.

In this paper, we introduce StreakNet-Arch, a real-time, end-to-end binary-classification framework based on our self-developed Underwater Carrier LiDAR-Radar (UCLR) that embeds Self-Attention and our novel Double Branch Cross Attention (DBC-Attention) to enhance scatter suppression. Under controlled water tank validation conditions, StreakNet-Arch with Self-Attention or DBC-Attention outperforms traditional bandpass filtering and achieves higher F₁ scores than learning-based MP networks and CNNs at comparable model size and complexity. Real-time benchmarks on an NVIDIA RTX 3060 show a constant Average Imaging Time (54 to 84 ms) regardless of frame count, versus a linear increase (58 to 1,257 ms) for conventional methods. To facilitate further research, we contribute a publicly available streak-tube camera image dataset contains 2,695,168 real-world underwater 3D point cloud data. More importantly, we validate our UCLR system in a South China Sea trial, reaching an error of 46mm for 3D target at 1,000 m depth and 20 m range. Source code and data are available at https://github.com/BestAnHongjun/StreakNet.

Avalanche photodiodes (APDs) based on InGaAs/InP are pivotal for applications in low-light detection, yet their performance is often hindered by edge breakdown and high dark currents. This study systematically optimizes guard ring structures to address these challenges, focusing on attached guard rings (AGRs) and floating guard rings (FGRs) through a synergistic approach combining simulation-guided design, fabrication, and experimental validation. We analyze the impact of Zn diffusion depth, AGR/FGR geometries, and electric field distribution on device performance. Experimental results demonstrate that optimized AGR structures reduce dark currents by 70% and enhance quantum efficiency (QE) by 43%, while FGR structures achieve an order-of-magnitude reduction in dark current and a 90% QE improvement compared to non-guarded devices. The breakdown voltage increases by 2.5 V (AGR) and 4 V (FGR), leading to enhanced gain. These advancements highlight the critical role of guard ring optimization in effectively mitigating edge breakdown, offering a pathway to high-sensitivity InGaAs/InP APDs for photon detection technologies.