Author Affiliations
Abstract
1 Laboratory of Infrared Materials and Devices, Research Institute of Advanced Technologies, Ningbo University, Ningbo 315211, China
2 Key Laboratory of Photoelectric Detection Materials and Devices of Zhejiang Province, Ningbo 315211, China
3 Advanced Optics & Photonics Laboratory, Department of Engineering, School of Science and Technology, Nottingham Trent University, Nottingham NG11 8NS, UK
4 School of Physics and Optoelectronic Engineering, Hangzhou Institute for Advanced Study, University of Chinese Academy of Sciences, Hangzhou 310024, China
5 Ningbo Institute of Oceanography, Ningbo 315832, China
We demonstrate a high-Q perfect light absorber based on all-dielectric doubly-resonant metasurface. Leveraging bound states in the continuum (BICs) protected by different symmetries, we manage to independently manipulate the Q factors of the two degenerate quasi-BICs through dual-symmetry perturbations, achieving precise matching of the radiative and nonradiative Q factors for degenerate critical coupling. We achieve a narrowband light absorption with a >600 Q factor and a > 99% absorptance at λ0 = 1550 nm on an asymmetric germanium metasurface with a 0.2λ0 thickness. Our work provides a new strategy for engineering multiresonant metasurfaces for narrowband light absorption and nonlinear applications.
resonant metasurface perfect light absorption bound states in the continuum Chinese Optics Letters
2024, 22(2): 023602
Author Affiliations
Abstract
1 Smart Computational Imaging Laboratory (SCILab), School of Electronic and Optical Engineering, Nanjing University of Science and Technolog, 210094, Nanjing Jiangsu Province, People’s Republic of China
2 Smart Computational Imaging Research Institute (SCIRI) of Nanjing University of Science and Technology, 210019, Nanjing Jiangsu Province, People’s Republic of China
3 Jiangsu Key Laboratory of Spectral Imaging Intelligent Sense, 210094, Nanjing Jiangsu Province, People’s Republic of China
4 Terahertz Technology Innovation Research Institute, University of Shanghai for Science and Technology, 200093 Shanghai, People’s Republic of China
5 School of Computer and Electronic Information, Nanjing Normal University, 210023, Nanjing Jiangsu Province, People’s Republic of China
6 Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut 06269, USA
Author Affiliations
Abstract
1 Smart Computational Imaging Laboratory (SCILab), School of Electronic and Optical Engineering, Nanjing University of Science and Technolog, 210094, Nanjing Jiangsu Province, People’s Republic of China
2 Smart Computational Imaging Research Institute (SCIRI) of Nanjing University of Science and Technology, 210019, Nanjing Jiangsu Province, People’s Republic of China
3 Jiangsu Key Laboratory of Spectral Imaging Intelligent Sense, 210094, Nanjing Jiangsu Province, People’s Republic of China
4 Terahertz Technology Innovation Research Institute, University of Shanghai for Science and Technology, 200093 Shanghai, People’s Republic of China
5 School of Computer and Electronic Information, Nanjing Normal University, 210023, Nanjing Jiangsu Province, People’s Republic of China
6 Department of Biomedical Engineering, University of Connecticut, 06269, Storrs Connecticut, USA
Quantitative phase imaging (QPI) has emerged as a valuable tool for biomedical research thanks to its unique capabilities for quantifying optical thickness variation of living cells and tissues. Among many QPI methods, Fourier ptychographic microscopy (FPM) allows long-term label-free observation and quantitative analysis of large cell populations without compromising spatial and temporal resolution. However, high spatio-temporal resolution imaging over a long-time scale (from hours to days) remains a critical challenge: optically inhomogeneous structure of biological specimens as well as mechanical perturbations and thermal fluctuations of the microscope body all result in time-varying aberration and focus drifts, significantly degrading the imaging performance for long-term study. Moreover, the aberrations are sample- and environment-dependent, and cannot be compensated by a fixed optical design, thus necessitating rapid dynamic correction in the imaging process. Here, we report an adaptive optical QPI method based on annular illumination FPM. In this method, the annular matched illumination configuration (i.e., the illumination numerical aperture (NA) strictly equals to the objective NA), which is the key for recovering low-frequency phase information, is further utilized for the accurate imaging aberration characterization. By using only 6 low-resolution images captured with 6 different illumination angles matching the NA of a 10x, 0.4 NA objective, we recover high-resolution quantitative phase images (synthetic NA of 0.8) and characterize the aberrations in real time, restoring the optimum resolution of the system adaptively. Applying our method to live-cell imaging, we achieve diffraction-limited performance (full-pitch resolution of $$655\,nm$$ at a wavelength of $$525\,nm$$ ) across a wide field of view ( $$1.77\,mm^2$$ ) over an extended period of time.
1 中国科学院 近代物理研究所, 兰州 730000
2 中国科学院大学 核科学与技术学院, 北京 100049
为满足分离扇回旋加速器（SSC）对于磁场精度的需求，需对其主场电源进行改造。提出开关电源与线性电源相结合的方式作为SSC主场电源的改造方案。电源总体分为两部分，采用模块化的开关电源作为前级电压源，三极管线性调整电路作为后级模块的主电路，充分利用两种电源的优势，实现高稳定度、低纹波的电流输出，同时大幅度提升电源的功率密度和可靠性。文章介绍了电源的工作原理及改造过程，详细阐述了三极管线性放大原理以及管压降控制电路、输出电流控制电路的设计与实现，通过仿真对电路进行功能验证，最终在电源样机上进行实验测试。测试结果表明：改造后主场电源输出电流稳定度达到了±3.99×10−6，电流纹波达到了2.7×10−9，各项性能均优于改造前。
加速器电源 高稳定度 低纹波 线性调整 accelerator power supply high stability low ripple linear adjustment 强激光与粒子束
2022, 34(6): 064003
张润南 1,2,3蔡泽伟 1,2,3,**孙佳嵩 1,2,3卢林芃 1,2,3[ ... ]左超 1,2,3,*
1 智能计算成像实验室, 南京理工大学电子工程与光电技术学院, 江苏 南京210094
2 南京理工大学智能计算成像研究院, 江苏 南京210019
3 江苏省光谱成像与智能感知重点实验室, 江苏 南京 210094
光场的相干性是定量衡量其产生显著的干涉现象所具备的重要物理属性。尽管高时空相干性的激光已成为传统干涉计量与全息成像等领域不可或缺的重要工具,但在众多新兴的计算成像领域(如计算摄像、计算显微成像),降低光源的相干性,即部分相干光源在获得高信噪比、高分辨率的图像信息方面具有独特优越性。因此,部分相干光场的“表征”与“重建”两方面问题的重要性日益凸显,亟需引入光场相干性理论及相干测量技术来回答计算成像中“光应该是什么”和“光实际是什么”的两大关键问题。在此背景下,系统地综述了光场相干性理论及相干测量技术,从经典的关联函数理论与相空间光学理论出发,阐述了对应的干涉相干测量法与非干涉相干恢复法的基本原理与典型光路结构;介绍了由相干测量所衍生出的若干计算成像新体制及其典型应用,如光场成像、非干涉相位复原、非相干全息术、非相干合成孔径、非相干断层成像等;论述了相干测量技术现阶段所面临的问题与挑战,并展望了其未来的发展趋势。
激光与光电子学进展
2021, 58(18): 1811003
1 福州大学机械工程及自动化学院, 福建 福州 350108
2 福建医科大学附属第一医院, 福建 福州 350005
光学相干断层扫描是目前检测糖尿病视网膜黄斑病变较为灵敏的方法之一,但病变的人工判断易产生主观失误,且比较耗时。为此,本文在迁移学习的基础上提出了一种改进的深度学习网络,用于视网膜图像的自动分类。先基于自适应阈值联合高斯滤波算法对图像进行预处理;然后以预训练模型为基础,通过微调解决样本差异的问题,并以全局平均池化方法替代传统的全连接层来提取深层特征,以降低网络的过拟合现象。基于实验数据对该网络进行验证,所提网络对视网膜病变图像的分类准确率可达97.3%,说明了所提网络对视网膜黄斑病变图像自动分类的有效性。
医用光学 光学相干断层扫描 迁移学习 高斯滤波 微调 全局平均池化 激光与光电子学进展
2021, 58(1): 0117002
1 福州大学机械工程及自动化学院, 福建 福州 350108
2 福建医科大学附属第一医院, 福建 福州 350000
针对光学相干层析视网膜图像进行人工分类诊断时存在漏检、效率低等问题,提出一种基于深度学习技术构建联合多层特征的卷积神经网络分类算法。首先通过均值漂移和数据归一化算法对视网膜图像进行预处理,并结合损失函数加权算法解决数据不平衡问题;其次使用轻量深度可分离卷积替代普通卷积层,降低模型参数量,采用全局平均池化替换全连接层,增加空间鲁棒性,并联合不同卷积层构建特征融合层,加强层间特征流通;最后使用SoftMax分类器进行图像分类。实验结果表明,该模型在准确率、精确率、召回率上分别达到97%、95%、97%,缩短了识别时长,所提方法在视网膜图像分类诊断中具有良好的性能。
图像处理 卷积神经网络 视网膜图像 特征融合 加权损失函数 激光与光电子学进展
2020, 57(24): 241025
Author Affiliations
Abstract
1 State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
2 National Laboratory of Solid State Microstructures, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
3 Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
4 e-mail: phytong@zju.edu.cn
A novel type of mid-IR microresonator, the chalcogenide glass (ChG) microfiber knot resonator (MKR), is demonstrated, showing easy fabrication, fiber-compatible features, resonance tunability, and high robustness. ChG microfibers with typical diameters around 3 μm are taper-drawn from glass fibers and assembled into MKRs in liquid without surface damage. The measured factor of a typical 824 μm diameter ChG MKR is about at the wavelength of 4469.14 nm. The free spectral range (FSR) of the MKR can be tuned from 2.0 nm (28.4 GHz) to 9.6 nm (135.9 GHz) by tightening the knot structure in liquid. Benefitting from the high thermal expansion coefficient of glass, the MKR exhibits a thermal tuning rate of at the resonance peak. When embedded in polymethyl methacrylate (PMMA) film, a 551 μm diameter MKR retains a factor of . The ChG MKRs demonstrated here are highly promising for resonator-based optical technologies and applications in the mid-IR spectral range.
Photonics Research
2020, 8(4): 04000616
兰州交通大学电子与信息工程学院, 甘肃 兰州 730070
BSCB模型在传输过程中引入Laplace算子时采用的点是某一像素周围4个邻点,对像素的表示会有局限性,进而造成修复后边缘模糊的现象。为优化这一问题,提出一种基于粗糙数据推理的改进BSCB算法,利用粗糙数据推理空间制定与某一像素相关联的采取规则以期挖掘像素之间的近似关系、衍生关系及拓展关系,选取与某一像素相关性最大的点,从而避免像素表示的局部性问题。实验结果表明,与经典的BSCB算法相比,改进后的算法在传输过程中采取的点更能体现图像结构,可获得较好的视觉效果,峰值信噪比也从数据层面证实修复效果的改善。
图像处理 图像修补 传输和扩散 Laplace算子 粗糙数据推理 BSCB算法 激光与光电子学进展
2019, 56(23): 231005
