Colliding of two counter-propagating laser pulses is a widely used approach to create a laser field or intensity surge. We experimentally demonstrate broadband coherent terahertz (THz) radiation generation through the interaction of colliding laser pulses with gas plasma. The THz radiation has a dipole-like emission pattern perpendicular to the laser propagation direction with a detected peak electric field 1 order of magnitude higher than that by single pulse excitation. As a proof-of-concept demonstration, it provides a deep insight into the physical picture of laser–plasma interaction, exploits an important option to the promising plasma-based THz source, and may find more applications in THz nonlinear near-field imaging and spectroscopy.

Ultra-broadband, intense, coherent terahertz (THz) radiation can be generated, detected, and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector, with a frequency coverage spanning across and beyond the whole “THz gap.” Such a research topic is termed “plasma-based THz wave photonics in gas and liquid phases.” In this paper, we review the most important experimental and theoretical works of the topic in the non-relativistic region with pump laser intensity below 1018W/cm2.

提出了一种用于单光子雪崩二极管图像传感器的超高速目标定位处理器。它由一个处理阵列，一个Y特征向量生成器和一个位置计算器组成，能够进行噪声减除和目标定位处理。设计了一种省略了乘法和减法运算的高斯滤波和背景减除法，降低了计算复杂度和硬件资源消耗，并显著地提高了处理速度。整个处理器在FPGA开发板上实现，实验结果表明，该处理器能够以100 000 帧/s的速度实时处理128×128分辨率的脉冲图像，并定位其中的运动物体。本文提出的处理器架构同样可用于其他脉冲图像传感器。

Recent moiré configurations provide a new platform for tunable and sensitive photonic responses, as their enhanced light–matter interactions originate from the relative displacement or rotation angle in a stacking bilayer or multilayer periodic array. However, previous findings are mostly focused on atomically thin condensed matter, with limitations on the fabrication of multilayer structures and the control of rotation angles. Structured microwave moiré configurations are still difficult to realize. Here, we design a novel moiré structure, which presents unprecedented capability in the manipulation of light–matter interactions. Based on the effective medium theory and S-parameter retrieval process, the rotation matrix is introduced into the dispersion relation to analyze the underlying physical mechanism, where the permittivity tensor transforms from a diagonal matrix to a fully populated one, whereas the permeability tensor evolves from a unit matrix to a diagonal one and finally becomes fully filled, so that the electromagnetic responses change drastically as a result of stacking and rotation. Besides, the experiment and simulation results reveal hybridization of eigenmodes, drastic manipulation of surface states, and magic angle properties by controlling the mutual rotation angles between two isolated layers. Here, not only a more precisely controllable bilayer hyperbolic metasurface is introduced to moiré physics, the findings also open up a new avenue to realize flat bands at arbitrary frequencies, which shows great potential in active engineering of surface waves and designing multifunctional plasmonic devices.

视觉芯片是一种高速、低功耗的智能视觉处理系统芯片，在生产生活中有广阔的应用前景。文中提出了一种新型的可编程视觉芯片架构，该架构的设计考虑了传统计算机视觉算法和卷积神经网络的运算特点，使其能够同时高效地支持这两类算法。该视觉芯片集成了可编程的多层次并行处理阵列、高速数据传输通路和系统控制模块，并采用65 nm标准CMOS工艺制程流片。测试结果表明：视觉芯片在200 MHz系统时钟下达到413GOPS的峰值运算性能，能够高效地完成包括完成人脸识别、目标检测等多种计算机视觉和人工智能算法。该视觉芯片在可编程度、运算性能以及能耗效率等方面都大大超越了其他视觉芯片。

采用频率为0.1 THz、功率密度为2.65 mW/cm 2的太赫兹光源分别辐射SD大鼠海马神经元5,15,25 min,通过神经元膜电位的变化,研究了太赫兹辐射对海马神经元兴奋性的影响,结果发现,15 min和25 min的太赫兹辐射会显著诱发海马神经元去极化,从而提高其兴奋性。为了探究太赫兹辐射提高神经元兴奋性的原因,检测了神经元内Ca 2+、Na +和K +浓度的变化,结果表明,此辐射使海马神经元内Ca 2+、Na +浓度增加,K +浓度减小。研究证实了太赫兹辐射(0.1 THz,2.65 mW/cm 2)通过调节海马神经元内带电离子的浓度促使其兴奋,为太赫兹辐射技术在生物医学领域应用的发展奠定了前期实验基础。