We report the effective slowing and trapping of Cs atoms in an ultrahigh-vacuum apparatus. The heated Cs atoms in an oven are slowed using a Zeeman slower after the oven chamber and then trapped using a magneto-optical trap in a science chamber. Compared to the traditional vacuum pressure of ~10^-7 Pa determined by the vapor pressure of Cs atoms in the oven chamber, the designed cold nipple and differential pumping tube are used between the oven and the oven chamber to achieve a lower vacuum pressure of ~3.6×10^-9 Pa. This is beneficial for achieving and maintaining an ultrahigh vacuum in the science chamber. We demonstrate the performance of our apparatus through the effective slowing of Cs atoms and an optimal magneto-optical trap.

The combination of an optical cavity and a proportional-integral (PI) controller is commonly used in experimental quantum optical fields. In this study, an optimal PI controller for an optical cavity was designed based on the average-squared value of the error signal. The controller was implemented using a field-programmable gate array (FPGA) data acquisition board and LabVIEW software. The overall gain of the controller is optimized by adopting the cavity transmission as an optical power reference, such that the cavity locking performance does not degrade as the optical power varies.

We experimentally demonstrate an 80-channel wavelength division multiplexing (WDM) transmission system over a 400 km fiber link. Raman amplification results in a non-flat WDM signal spectrum. Therefore, bit allocation optimization is used to enable different channels to carry different order quadrature amplitude modulation signals according to their optical signal-noise-ratios. A neural network equalizer based on a convolutional neural network (CNN), long short-term memory (LSTM) network, and fully connected (FC) layer structure is adopted in Rx digital signal processing, in which CNN is used for characteristic extraction, LSTM is used for equalization and demodulation, and FC layers are used for output. After transmission, the bit error rate of all channels is below the 25% soft-decision forward error correction threshold, and the line rate reaches 53.76 Tbit/s.We experimentally demonstrate an 80-channel wavelength division multiplexing (WDM) transmission system over a 400 km fiber link. Raman amplification results in a non-flat WDM signal spectrum. Therefore, bit allocation optimization is used to enable different channels to carry different order quadrature amplitude modulation signals according to their optical signal-noise-ratios. A neural network equalizer based on a convolutional neural network (CNN), long short-term memory (LSTM) network, and fully connected (FC) layer structure is adopted in Rx digital signal processing, in which CNN is used for characteristic extraction, LSTM is used for equalization and demodulation, and FC layers are used for output. After transmission, the bit error rate of all channels is below the 25% soft-decision forward error correction threshold, and the line rate reaches 53.76 Tbit/s.

We investigate off-axis phase-matched terahertz (THz) radiation in laser plasma pumped by few-cycle laser pulses. We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse's focal carrier-envelope phase (CEP). Ring-like profiles of THz radiation are obtained at CEP values of 0.5 π and 1.5 π, due to the inversely symmetric local THz waveforms emitted before and after laser focus. Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.We investigate off-axis phase-matched terahertz (THz) radiation in laser plasma pumped by few-cycle laser pulses. We find that the THz amplitude and angular distributions in the far field are sensitively dependent on the pump pulse's focal carrier-envelope phase (CEP). Ring-like profiles of THz radiation are obtained at CEP values of 0.5 π and 1.5 π, due to the inversely symmetric local THz waveforms emitted before and after laser focus. Off-axis phase-matched THz radiation offers a tool to accurately measure the CEP of few-cycle pulses at the center of a medium.

In this paper we report a compact and robust regenerative amplifier developed as the pump laser for a high repetition rate terahertz parametric amplifier. With properly chosen pump source and carefully designed cavity, Nd∶YVO₄ crystal, and laser beam collimator, a maximum output pulse energy of 480 μJ has been achieved at the repetition rate of 10 kHz. The output laser has a nearly Gaussian transverse profile and a narrow bandwidth of 0.2 nm. Long-term monitoring shows an root mean square power fluctuation of about 1%. These characteristics satisfy all requirements for high repetition rate terahertz parametric amplifier.

针对传统光谱偏振成像需要动态调制、光通量低和光谱分辨率有限等问题,提出了基于计算光谱成像和像素级偏振探测的成像新方法,以双通道形式单次成像获取目标高分辨率的空间、光谱和偏振信息。搭建了编码孔径光谱偏振成像通道和偏振成像通道的双路实验装置,得到了450~650 nm范围内25个波段在4种偏振态下的光谱数据立方体,以及每个波段的偏振度和偏振角。所提方法的光谱分辨率优于10 nm,光谱重构精度约为86.3%,相对单路成像方法,光谱重构精度提升了10.5个百分点。

2018年5月8日至11日, 第4届纳米发电机与压电电子学国际会议(NGPT 2018)在韩国首尔成均馆大学隆重召开, 来自全球17个国家和地区的400余位专家学者及各方代表齐聚一堂, 共同探讨微纳能源领域最新科研进展。会议主题分为3大类, 包括纳米发电机、压电电子学和摩擦电子学、纳米发电机的材料和电路设计, 共有315篇投稿。本文将从微能源采集技术的理论、材料和应用等角度, 详细介绍和阐述相关领域的研究现状与突出成果, 并对产业发展趋势进行总结与展望。

2018年5月8日至11日, 第4届纳米发电机与压电电子学国际会议(NGPT 2018)在韩国首尔成均馆大学隆重召开, 来自全球17个国家和地区的400余位专家学者及各方代表齐聚一堂, 共同探讨微纳能源领域最新科研进展。会议主题分为3大类, 包括纳米发电机、压电电子学和摩擦电子学、纳米发电机的材料和电路设计, 共有315篇投稿。本文将从微能源采集技术的理论、材料和应用等角度, 详细介绍和阐述相关领域的研究现状与突出成果, 并对产业发展趋势进行总结与展望。

《基于激光诱导及散斑图像处理的航空发动机尾气粒子流场监测关键技术研究》国家自然科学基金委员会与中国民用航空局联合项目(项目编号：U1533111)采用激光诱导白炽光的方法向航空发动机尾气区域发射高功率激光, 激光聚焦区域的尾气粒子将产生高温炽化现象并形成白炽散斑。采用双目视觉测量系统对炽化区域粒子的流场分布进行测量与监控, 建立发动机尾气粒子三维流场分布模型与发动机运行状态之间的关系, 系统测量原理示意图如图1所示。