Ex situ characterization techniques in molecular beam epitaxy (MBE) have inherent limitations, such as being prone to sample contamination and unstable surfaces during sample transfer from the MBE chamber. In recent years, the need for improved accuracy and reliability in measurement has driven the increasing adoption of in situ characterization techniques. These techniques, such as reflection high-energy electron diffraction, scanning tunneling microscopy, and X-ray photoelectron spectroscopy, allow direct observation of film growth processes in real time without exposing the sample to air, hence offering insights into the growth mechanisms of epitaxial films with controlled properties. By combining multiple in situ characterization techniques with MBE, researchers can better understand film growth processes, realizing novel materials with customized properties and extensive applications. This review aims to overview the benefits and achievements of in situ characterization techniques in MBE and their applications for material science research. In addition, through further analysis of these techniques regarding their challenges and potential solutions, particularly highlighting the assistance of machine learning to correlate in situ characterization with other material information, we hope to provide a guideline for future efforts in the development of novel monitoring and control schemes for MBE growth processes with improved material properties.

We introduce a novel method to create mid-infrared (MIR) thermal emitters using fully epitaxial, metal-free structures. Through the strategic use of epsilon-near-zero (ENZ) thin films in InAs layers, we achieve a narrow-band, wide-angle, and p-polarized thermal emission spectra. This approach, employing molecular beam epitaxy, circumvents the complexities associated with current layered structures and yields temperature-resistant emission wavelengths. Our findings contribute a promising route towards simpler, more efficient MIR optoelectronic devices.

相对论电子束在理想顺磁环境下能够以较高的注量率击中靶目标，但实际情况中由于受环境的影响，相对论电子束的传输方向可能会与地磁场呈小角度偏差，因此会受到地磁场的作用产生拉莫尔进动，影响电子束的到靶瞄准以及到靶注量。基于二维片状相对论电子束，分别对相对论电子束顺磁和偏离磁场3°角两种传输情况进行仿真模拟，通过模拟束团的传输过程，分析研究了顺磁环境下不同传输距离束团到靶率的变化规律，以及偏离磁场3°角时传输过程中注量率的变化规律，为相对论电子束到靶率的预估和靶目标的瞄准提供数据参考。

Orbital-angular-momentum (OAM) multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links. The coherent beam combining (CBC) system can simultaneously realize OAM multiplexing and achieve high-power laser output, providing substantial advantages for long-distance communication. Herein, we present an integrated CBC system for free-space optical links based on OAM multiplexing and demultiplexing technologies for the first time, to the best of our knowledge. A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally. The experimental results exhibit a low bit error rate of 0.47% and a high recognition precision of 98.58% throughout the entire data transmission process. By employing such an ingenious strategy, this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.

在光场中引入一维燕尾突变函数，利用分步傅立叶方法研究了燕尾高斯（SG）光束在分数薛定谔方程（FSE）中的演化动力学，详细讨论了线性势、抛物线势、高斯势及无势的情况。在无势情况下，SG光束会因群延迟的变化而分裂成两个子光束，并且分裂轨迹会随着Lévy指数的增大出现弯曲。在线性势下，SG光束出现了周期性反转和聚焦行为，Lévy指数和线性势系数分别影响聚焦点峰值强度和反转及聚焦的演化周期，其反转和聚焦周期距离只受线性势影响而与Lévy指数无关。在抛物线势情况下，具有较大Lévy指数的SG光束的主瓣和旁瓣反转和聚焦从杂乱转变为周期性演化，其反转聚焦位置由抛物线势系数和Lévy指数共同决定。在高斯势中，光束的演化在势垒的约束下由于反射主瓣和旁瓣的干扰，窄势垒的周期性反转和聚焦出现杂乱混沌现象，而对于宽势垒，由于旁瓣减弱，周期性演化变得清晰。本文研究结果为利用高阶燕尾光波场实现光调制器和光开关提供了可能。