Author Affiliations
Abstract
1 State Key Laboratory of Information Photonics and Optical Communications, School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China
2 Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3 Beijing Computational Science Research Center, Beijing 100193, China
4 School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100083, China
5 e-mail: mlei@bupt.edu.cn
6 e-mail: limin.liu@csrc.ac.cn
Two-dimensional (2D) materials with potential applications in photonic and optoelectronic devices have attracted increasing attention due to their unique structures and captivating properties. However, generation of stable high-energy ultrashort pulses requires further boosting of these materials’ optical properties, such as higher damage threshold and larger modulation depth. Here we investigate a new type of heterostructure material with uniformity by employing the magnetron sputtering technique. Heterostructure materials are synthesized with van der Waals heterostructures consisting of and . The bandgap, carrier mobility, and carrier concentration of the heterostructure materials are calculated theoretically. By using these materials as saturable absorbers (SAs), applications in fiber lasers with -switching and mode-locking states are demonstrated experimentally. The modulation depth and damage threshold of SAs are measured to be 64.17% and , respectively. Both theoretical and experimental results indicate that heterostructure materials have large modulation depth, and can resist high power during the generation of ultrashort pulses. The heterostructure materials have the advantages of low cost, high reliability, and suitability for mass production, and provide a promising solution for the development of 2D-material-based devices with desirable electronic and optoelectronic properties.
Nonlinear optical materials Mode-locked lasers Lasers, fiber Photonics Research
2018, 6(3): 03000220
目前雷达情报数据传输以短波电台和光纤通信为主, 这些传输手段遭到破坏后通信容量将会极大降低。为解决低通信容量下的航迹数据传输问题, 提出了一种基于航迹数据曲线拟合的数据压缩方法。雷达探测目标得到点迹, 然后将点迹关联形成航迹, 先对航迹进行曲线拟合得到拟合曲线参数。通过传输拟合曲线参数来代替传输航迹数据, 最终利用拟合曲线参数恢复出航迹, 从而极大压缩数据传输量, 完成在低通信容量下的雷达航迹数据传输。
航迹拟合 数据压缩 雷达 数据传输 低通信容量 track fitting data compression radar data transmission low transmission capacity
1 武汉大学遥感信息工程学院, 湖北 武汉430079
2 首都师范大学资源环境与旅游学院, 北京100048
3 首都师范大学城市环境过程与数字模拟国家重点实验室培育基地, 北京100048
针对常规极化SAR影像监督分类在分类时由于极化信息利用不完全, 导致分类结果不可信的缺陷, 在分析地物极化散射特性的基础上, 提出一种结合复Wishart分类器思想的极化SAR监督分类方法, 在监督分类的基础上, 利用几乎包含所有极化信息的相干矩阵进行后续分类, 利用地物所有极化散射信息完成类别的划分。 首先, 利用Cloude&Pottier极化特征组合对影像进行监督分类, 获得初始类别划分结果； 为纠正监督分类时仅利用特征矢量的空间分布特性进行类别划分导致的错误, 对监督分类结果精度评价及研究区地物散射相似性分析, 综合确定初始分类结果中分类效果较差、 待后续调整类别的像素集； 然后以各类别的相干矩阵均值为初始聚类中心, 利用核模糊C均值算法, 结合相干矩阵的复Wishart分布特性, 对待修正的像素集进行后续类别迭代调整, 获得精细分类结果。 采用国产X-SAR获取的海南陵水地区的全极化SAR影像进行分类试验, 结果表明: 提出的对极化SAR影像监督分类后利用地物散射特性相似性对错分像素重新进行聚类调整类别的方法, 与仅进行监督分类相比, 分类结果总体精度更高, 也更满足地物的散射特性。
监督分类 T3聚类中心 散射特性 复Wishart分布 后续类别调整 Supervised classfication T3 clustering center Scattering characters Complex Wishart distribution Subsequent category iteration
