1 东华大学 理学院，上海 201620
2 中国科学院上海光学精密机械研究所 空间激光信息传输与探测技术重点实验室，上海 201800
海洋是全球碳循环过程中的重要环节，从浮游植物光合作用开始，碳在海洋中沿食物链传递，以颗粒有机碳（POC）形式存在。对海洋中颗粒有机碳含量的探测，将对海洋碳汇能力的评估起到重要作用。在干净大洋水体中，激光雷达可根据浮游植物引起的光学性质变化实现剖面信息的探测，因此对基于高光谱分辨率技术的海洋颗粒有机碳浓度剖面探测系统性能进行了仿真分析。利用激光雷达方程对探测系统在大洋水体的最大探测深度进行了仿真；利用碘分子吸收池作滤波器，并结合大洋水体的透射窗口和激光器的工程设计，分析了不同载荷平台下探测系统的最佳工作波长。仿真结果表明，在满足单次探测系统信噪比为5的探测要求时，大洋水体50 dB动态范围下的探测深度平均在80 m；船载、机载平台探测系统最佳工作波长为532.245 1 nm和532.292 8 nm。
激光雷达 海洋POC探测 碘池滤波 性能仿真 lidar ocean POC detection iodine pool filter performance simulation 红外与激光工程
2023, 52(5): 20220715
Author Affiliations
Abstract
1 Nanjing University of Posts and Telecommunications, College of Electronic and Optical Engineering & College of Flexible Electronics (Future Technology), Nanjing, China
2 Nanjing University, School of Electronic Science and Engineering, Nanjing, China
The AlGaN/GaN p–n junction has received extensive attention due to its capability of rapid photogenerated carrier separation in photodetection devices. The AlGaN/GaN heterojunction nanowires (NWs) have been especially endowed with new life for distinctive transport characteristics in the photoelectrochemical (PEC) detection field. A self-powered PEC ultraviolet photodetector (PEC UV PD) based on the p-AlGaN/n-GaN heterojunction NW is reported in this work. The n-GaN NW layer plays a crucial role as a current flow hub to regulate carrier transport, which mainly acts as a light absorber under 365 nm and carrier recombination layer under 255 nm illumination, which can effectively modulate photoresponsivity at different wavelengths. Furthermore, by designing the thicknesses of the NW layer, the photocurrent polarity reversal was successfully achieved in the constructed AlGaN/GaN NW PEC UV PD at two different light wavelengths. In addition, by combining with platinum decoration, the photoresponse performance could be further enhanced. Our work provides insight into transport mechanisms in the AlGaN/GaN NW PEC system, and offers a feasible and comprehensive strategy for further exploration of multifunctional optoelectronic devices.
GaN nanowires ultraviolet detection photoelectrochemistry photoresponse Advanced Photonics Nexus
2023, 2(3): 036003
1 成都理工大学地球科学学院，四川 成都 610059
2 成都理工大学地质灾害防治与地质环境保护国家重点实验室，四川 成都 610059
近年来，以卷积神经网络为代表的深度学习方法因不用进行复杂的数据预处理和特征设计逐渐成为高光谱图像分类领域的研究热点。在现有的神经网络模型基础上，结合高光谱图像数据特点，提出了一种注意力卷积神经网络模型。该模型通过残差结构构建深度卷积神经网络提取空谱特征，引入通道注意力机制对提取的特征进行重标定。根据特征重要性的不同，注意力机制对不同通道上的特征赋予不同的权重，突出重要特征，抑制次要特征，从而提高分类的精度。在两个公开的高光谱数据集Indian Pines和Pavia University上进行了实验。当数据集的空间邻域大小设置为19×19，Indian Pines以3∶1∶6的比例划分样本，Pavia University以1∶1∶8的比例划分样本时，数据集的分类精度最优，平均总体分类精度为99.55%，平均分类精度为99.31%，平均Kappa系数为99.45%。实验结果表明，引入残差结构的深度卷积神经网络可以提取高光谱图像的深层空谱特征，注意力机制对特征进行重新标定，强化了重要特征，从而有效提高了高光谱图像的分类精度。
成像系统 高光谱图像 卷积神经网络 残差结构 注意力机制 激光与光电子学进展
2022, 59(18): 1811001
1 东华大学理学院，上海 201620
2 中国科学院上海光学精密机械研究所空间激光信息技术研究中心，上海 201800
3 中国科学院空间激光信息传输与探测技术重点实验室，上海 201800
海洋温度和盐度是重要的海洋环境参数，对了解海洋性质、生物多样性具有重要作用。本文基于碘分子吸收池的边缘探测技术，将携带有温度信息的布里渊散射光分为三束，这三束光分别通过三个压强不同的碘分子吸收池，形成三个探测通道，得到两个信号的强度比值信息；之后利用迭代算法即可同时反演出被测区域的温度和盐度信息。采用探测器输出信号强度比值的形式能有效抑制激光器光强抖动带来的影响。为将测温误差控制在0.2 K以内，所提算法对探测器输出强度比值的随机抖动程度为1.3‰。本技术路线具有不受入射角影响、测量速度快、无需事先知晓盐度信息等优势，有望应用于机载、星载等移动平台上。
测量 碘分子吸收池 边缘探测 温度反演 信号强度比值 抖动
Author Affiliations
Abstract
The computed tomography imaging of a local region inside a sample with a size larger than the field of view is particularly important for synchrotron X-ray imaging. In this letter, an improved algorithm is proposed to reconstruct the local structure inside a sample using almost completely local data. The algorithm significantly reduces the X-ray radiation dose and improves computational efficiency. Simulation results show that the new algorithm works well and has a higher reconstruction precision than previous methods, as confirmed by experimental results carried out at the Shanghai Synchrotron Radiation Facility.
340.7440 X-ray imaging 110.6960 Tomography 100.3010 Image reconstruction techniques 340.6720 Synchrotron radiation Chinese Optics Letters
2014, 12(2): 023401
