An optical probing of laser–plasma interactions can provide time-resolved measurements of plasma density; however, single-shot and multi-frame probing capabilities generally rely on complex setups with limited flexibility. We have demonstrated a new method for temporal resolution of the rapid dynamics ( $\sim 170$ fs) of plasma evolution within a single laser shot based on the generation of several consecutive probe pulses from a single beta barium borate-based optical parametric amplifier using a fraction of the driver pulse with the possibility to adjust the central wavelengths and delays of particular pulses by optical delay lines. The flexibility and scalability of the proposed experimental technique are presented and discussed.

为了实现集成电路内部电信号波形的非接触探测，设计了基于共光路干涉仪的探测光路，同时利用锁相放大技术噪声抑制能力强，灵敏度高的特点，提出了基于锁相放大的信号处理方法提取反射光中携带的微弱器件电光信号。该方法利用器件电光信号强度随器件电信号周期性变化的特点，首先将来自光电探测器的电信号进行锁相放大处理消除大部分噪声，然后再利用平均处理技术进一步抑制外界噪声干扰，提高器件电光信号的信噪比，从而将淹没在噪声中的器件电光信号提取出来，重建器件内部电学信息。利用该探测方法成功探测到芯片内部动态工作电流在μA量级的电路节点电光信号，信噪比达到4.99 dB，而仅使用平均处理技术得到的信号信噪比只有-44.29 dB。研究内容为集成电路内部电信号的光学探测提供了一种新的思路，未来可在集成电路动态缺陷检测领域得到应用。

In order to understand the transport of fast electrons within solid density targets driven by an optical high power laser, we have numerically investigated the dynamics and structure of strong self-generated magnetic fields in such experiments. Here we present a systematic study of the bulk magnetic field generation due to the ponderomotive current, Weibel-like instability and resistivity gradient between two solid layers. Using particle-in-cell simulations, we observe the effect of varying the laser and target parameters, including laser intensity, focal size, incident angle, preplasma scale length, target thickness and material and experimental geometry. The simulation results suggest that the strongest magnetic field is generated with laser incident angles and preplasma scale lengths that maximize laser absorption efficiency. The recent commissioning of experimental platforms equipped with both optical high power laser and X-ray free electron laser (XFEL), such as European XFEL-HED, LCLS-MEC and SACLA beamlines, provides unprecedented opportunities to probe the self-generated bulk magnetic field by X-ray polarimetry via Faraday rotation with simultaneous high spatial and temporal resolution. We expect that this systematic numerical investigation will pave the way to design and optimize near future experimental setups to probe the magnetic fields in such experimental platforms.

The ultrafast charge dynamics following the interaction of an ultra-intense laser pulse with a foil target leads to the launch of an ultra-short, intense electromagnetic (EM) pulse along a wire connected to the target. Due to the strong electric field (of the order of $\text{GV m}^{-1}$) associated to such laser-driven EM pulses, these can be exploited in a travelling-wave helical geometry for controlling and optimizing the parameters of laser accelerated proton beams. The propagation of the EM pulse along a helical path was studied by employing a proton probing technique. The pulse-carrying coil was probed along two orthogonal directions, transverse and parallel to the coil axis. The temporal profile of the pulse obtained from the transverse probing of the coil is in agreement with the previous measurements obtained in a planar geometry. The data obtained from the longitudinal probing of the coil shows a clear evidence of an energy dependent reduction of the proton beam divergence, which underpins the mechanism behind selective guiding of laser-driven ions by the helical coil targets.