Author Affiliations
Abstract
1 Quantum Sensing Center, Zhejiang Lab, Hangzhou 310000, China
2 State Key Laboratory of Modern Optical Instruments, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
3 e-mail: fuzhenhai@zju.edu.cn
4 e-mail: gaoxw@zhejianglab.com
5 e-mail: huhuizhu2000@zju.edu.cn
The nanomechanical resonator based on a levitated particle exhibits unique advantages in the development of ultrasensitive electric field detectors. We demonstrate a three-dimensional, high-sensitivity electric field measurement technology using the optically levitated nanoparticle with known net charge. By scanning the relative position between nanoparticle and parallel electrodes, the three-dimensional electric field distribution with microscale resolution is obtained. The measured noise equivalent electric intensity with charges of reaches the order of at . Linearity analysis near resonance frequency shows a measured linear range over 91 dB limited only by the maximum output voltage of the driving equipment. This work may provide an avenue for developing a high-sensitivity electric field sensor based on an optically levitated nano-resonator.
Photonics Research
2023, 11(2): 279
江苏方天电力技术有限公司，江苏 南京 211103
传感器是配电物联网的基础，尤其是基于布里渊散射的分布式光纤传感器应用日益广泛。为了提高基于布里渊散射的分布式光纤传感的测量速度，为基于温度的电气设备状态感知奠定基础，对单斜坡法在光纤沿线温度测量的适用性进行了研究。编程实现了基于伪Voigt模型的谱拟合法和单斜坡法的计算机程序，针对不同信噪比的布里渊谱分别采用谱拟合法和单斜坡法计算光纤沿线的温度。结果表明，在一定的信噪比和光纤沿线布里渊频移波动程度范围内，单斜坡法的计算准确性可以达到与谱拟合法相近程度，但谱测量时间可以缩短为后者的几十分之一，对应的计算时间仅为谱拟合法的1/758。研究了信噪比、布里渊频移和线宽不确定度对误差的影响，结果表明，随信噪比（以dB为单位）增加，温度误差快速下降，然后逐渐趋于稳定值；随布里渊频移与工作点差距的增加，温度误差增大，且加速度随二者差距的增大而增大；温度误差随线宽偏差的增大而增大。
分布式光纤传感 布里渊频移 单斜坡法 温度 distributed optical fiber sensing Brillouin frequency shift slope-assisted technique temperature
为了提高基于布里渊散射的分布式光纤传感系统实时性, 在分析经典基于洛伦兹和伪Voigt模型拟合法优缺点的基础上, 将多层前馈神经网络方法用于布里渊频移的估算。确定了神经网络的结构、输入及输出量、激活函数和训练算法, 采用不同信噪比(5dB~40dB)和布里渊频移(10.62GHz~10.82GHz)的布里渊谱训练该网络, 训练完成后网络针对训练样本的布里渊频移预测误差仅约为1MHz, 同时也训练了径向基函数神经网络。针对温度和应变沿线波动的布里渊谱分别采用以上训练得到的多层前馈神经网络、径向基函数神经网络、基于洛伦兹模型的谱拟合法和基于伪Voigt模型的谱拟合法估算光纤沿线的布里渊频移并解调获得光纤沿线的温度和应变。结果表明, 多层前馈神经网络方法的准确性与经典的基于洛伦兹模型和伪Voigt模型的谱拟合法相似, 但计算时间仅为后两者的1/947.16~1/470.95和1/784.56~1/532.88。该研究为基于布里渊散射的光纤温度和应变快速测量提供了参考。
传感器技术 温度和应变 神经网络 解调 快速 sensor technique temperature and strain artificial neural network demodulation fast
南京航空航天大学 航天学院, 江苏 南京 210000
鉴于气浮台姿态测量是实现气浮台控制的重要基础, 为了实现三轴气浮台姿态准确、快速测量, 提出一种基于单目视觉的实时、高精度的姿态测量方法。采取一种鲁棒性强的三轴气浮台靶标形状及布局来提高姿态获取精度。提出一种拟合圆心流程, 通过粗获取与精获取方法对靶标进行实时、鲁棒跟踪。最后利用提取到的圆心位置信息采用迭代最小二乘的姿态估计算法解算出气浮台的位姿信息。实验结果表明: 单目视觉测量算法的实时帧数可达20帧, 静态姿态测量精度约为0.02°, 动态姿态测量精度约为0.12°, 能够满足气浮台对姿态测量时的实时性、准确性、鲁棒性需求。
三轴气浮台 单目视觉 靶标识别 姿态估计 Three-axis air bearing table monocular vision target recognition attitude estimation
三轴气浮台的冷气系统设计直接影响到控制系统的精度和冷气消耗量。对三轴气浮台冷气控制中的推力分配问题进行了研究，针对冗余的推力分配问题，设计了两种可以优化三轴气浮台推力分配的方法，从经济性、精确性等多个角度对推力分配进行了相应的理论分析和实验研究。通过数学仿真和实验验证了所提方法的合理性和有效性，研究结果满足了在给出期望力矩后能够快速找到较优的冷气推力分配方案的要求，简化了推力分配的步骤，并且有效解决了推力器冗余分配造成冷气浪费的问题，同时使冷气控制精度在设计范围内。最后的实验结果显示冷气控制下稳定误差在0.4°以内，完成了一次只用4个推力器实现姿态控制的任务。
三轴气浮台 冷气系统 推力分配 优化算法 查表法 three-axis air bearing test bed air conditioning system thrust allocation optimization algorithm table look-up strategy
Author Affiliations
Abstract
1 School of Science, East China University of Technology, Nanchang 330013, China
2 Department of Physics, National University of Defense Technology, Changsha 410073, China
3 School of Science, East China Jiaotong University, Nanchang 330013, China
4 State Key Laboratory of High Field Laser Physics and CAS Center for Excellence in Ultra-intense Laser Science, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences (CAS), Shanghai 201800, China
5 State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
Molecular ions, produced via ultrafast ionization, can be quantum emitters with the aid of resonant electronic couplings, which makes them the ideal candidates to study strong-field quantum optics. In this work, we experimentally and numerically investigate the necessary condition for observing a collective emission arising from macroscopic quantum polarization in a population-inverted gain system, uncovering how the individual ionic emitters proceed into a coherent collection within hundreds of femtoseconds. Our results show that for a relatively high-gain case, the collective emission behaviors can be readily initiated for all the employed triggering pulse area. However, for a low-gain case, the superradiant amplification is quenched since the building time of macroscopic interionic quantum coherence exceeds the dipole dephasing time, in which situation the seed amplification and free induction decay play an essential role. These findings not only clarify the contentious key issue regarding to the amplification mechanism of lasing but also show the unique characteristics of ultrashort laser-induced amplification in a molecular ion system where both the microscopic and macroscopic quantum coherence might be present.
Photonics Research
2021, 9(10): 10002046
1 西安理工大学电子工程系，西安 710048
2 西安电子科技大学微电子学院，西安 710071
利用水平热壁CVD方法，基于SiH4C3H8H2生长系统在n型4HSiC偏4°衬底上进行同质外延生长。通过Nomarski光学显微镜、激光共聚焦显微镜和拉曼散射光谱(Raman)，对外延层中的新形貌三角形缺陷——顶端有倒金字塔结构的三角形缺陷(IPRTD)的表面形貌、结构进行了表征，并根据表征结果提出了该新形貌三角形缺陷的产生机理。研究结果表明，IPRTD由3CSiC晶型构成；在外延生长中，位于IPRTD生长方向上游的位错缺陷所引起的表面吸附原子的2D成核生长是导致3CSiC晶型出现的主要原因。同时，外延生长过程中，生长速率和氢气刻蚀作用在［112-0］和［11-00］/［1-100］方向上的差异是导致IPRTD顶端具有倒金字塔结构的主要原因。
同质外延生长 三角形缺陷 形成机理 4HSiC 4HSiC homoepitaxial growth triangular defect formation mechanism
随着航天遥感技术的发展, 对海洋船舶快速检测识别需求日益增长。基于深度学习提出了一种结合高低分辨率遥感图像的船舶目标检测方法。该方法首先使用YOLO v3模型对宽幅、低分辨率卫星遥感图像中的目标船舶进行快速筛查, 然后针对高分辨率卫星遥感图像信息, 提出了一种基于注意力机制的RetinaNet模型对目标船舶进行精确匹配与分类。仿真实验结果表明, 这种改进的RetinaNet模型在目标检测中具有很好的效果, 使用两种分辨率的卫星进行协同工作能够有效提升工作效率。
遥感图像 目标检测 船舶检测 注意力机制 remote sensing image target detection ship detection YOLO v3 YOLO v3 RetinaNet RetinaNet attention mechanism
Author Affiliations
Abstract
1 School of Science, East China University of Technology, Nanchang 330013, China
2 State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
3 School of Science, East China Jiaotong University, Nanchang 330013, China
4 Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
We report on an experimental investigation on the dynamic decoherence process of molecular rotational wavepackets during femtosecond laser filamentation based on time-dependent mean wavelength shifts of a weak probe pulse. Details of periodic revival structures of transient alignment can be readily obtained from the measured shifted spectra due to the periodic modulation of the molecular refractive index. Using the method, we measured decoherence lifetimes of molecular rotational wavepackets in N2 and O2 under different experimental conditions. Our results indicate that decoherence lifetimes of molecular rotational wavepackets are primarily determined by the relative population of rotational states in the wave packet and intermolecular collisions, rather than the focusing intensity.
020.2649 Strong field laser physics 300.6530 Spectroscopy, ultrafast Chinese Optics Letters
2018, 16(12): 120201
南京航空航天大学 航天学院, 江苏 南京 210016
非合作目标航天器的位姿测量一直是各类复杂航天任务中所需解决的关键难题之一。传统的姿态测量算法多采用欧拉角以及旋转矩阵的方式描述目标位姿, 计算参数较多, 算法形式也相对复杂。针对这个问题, 通过单目视觉识别出具有矩形结构特征的目标航天器的一个矩形面, 然后在马达代数框架下, 根据该矩形面两条平行边所在直线方程的差值信息直接计算出目标姿态参数, 最终将姿态解算问题简化为一组四元线性方程组的求解。该算法无需知道目标尺寸, 计算形式简洁, 实时性高, 同时也能很好地保证结果的正交性。数值仿真以及地面验证实验结果表明, 该算法具有较强的稳定性, 测量精度能够满足测控要求, 在交会近距离范围内受两航天器间相对距离的影响较小。
马达代数 姿态测量 非合作目标 单目视觉 motor algebra attitude determination non-cooperative target spacecraft monocular vision
