Author Affiliations
Abstract
National Key Laboratory of Scattering and Radiation, Beijing 100854, China
Controlling the dispersion characteristic of metasurfaces (or metalenses) along a broad bandwidth is of great importance to develop high-performance broadband metadevices. Different from traditional lenses that rely on the material refractive index along the light trajectory, metasurfaces or metalenses provide a new regime of dispersion control via a sub-wavelength metastructure, which is known as negative chromatic dispersion. However, broadband metalenses design with high-performance focusing especially with a reduced device dimension is a significant challenge in society. Here, we design, fabricate, and demonstrate a broadband high-performance diffractive-type plasmonic metalens based on a circular split-ring resonator metasurface with a relative working bandwidth of 28.6%. The metalens thickness is only ( is at the central wavelength), which is much thinner than previous broadband all-dielectric metalenses. The full-wave simulation results show that both high transmissive efficiency above 80% (the maximum is even above 90%) and high average focusing efficiency above 45% (the maximum is 56%) are achieved within the entire working bandwidth of 9–12 GHz. Moreover, an average high numerical aperture of 0.7 () of high-efficiency microwave metalens is obtained in the simulations. The broadband high-performance metalens is also fabricated and experimental measurements verify its much higher average focusing efficiency of 55% (the maximum is above 65% within the broad bandwidth) and a moderate high NA of 0.6. The proposed plasmonic metalens can facilitate the development of wavelength-dependent broadband diffractive devices and is also meaningful to further studies on arbitrary dispersion control in diffractive optics based on plasmonic metasurfaces.
Photonics Research
2024, 12(4): 813
Author Affiliations
Abstract
The key Laboratory of Optoelectronic Technology & System (Ministry of Education), Chongqing University, Chongqing 400044, China
In this study, we present a dual-Fizeau-interferometer-based high-speed and wide-range fiber-optic Fabry-Perot (F-P) demodulation system. We employ two Fizeau interferometers with air cavity thickness satisfying the quadrature requirement to increase the demodulation speed and broaden the demodulation range in order to address the issues of the existing fiber F-P demodulation system’s sluggish demodulation rate and limited range. In order to investigate the demodulation properties of the dual-Fizeau-interferometer-based demodulation system, we derive and create a theoretical model of the system. The theoretical model, which primarily consists of the structural design of the interferometer and the study of the center wavelength of the light sources and their bandwidth selection, is used to construct the optical structure of the demodulation system. According to the calculation results, the demodulated signal exhibits the best contrast ratio when the two light sources’ respective center wavelengths are 780 nm and 850 nm, and their bandwidths are 28 nm and 30 nm. Finally, we finish evaluating the demodulation system’s demodulation performance, parameter calibration, and assembly debugging. The test results demonstrate the constant operation of the demodulation system, an update rate of 100 kHz, a demodulation range of 4.74 μm, and a cavity length resolution of approximately 5 nm. Additionally, the system can perform high speed demodulation thanks to the light emitting diode’s (LED’s) nanosecond level switching speed and the usage of a single point detector.
Fiber-optic Fabry-Perot sensor Fizeau interferometer LED optical path difference quadrature requirement Photonic Sensors
2023, 13(2): 230229
长春理工大学 电子信息工程学院,吉林 长春 130022
针对近红外图像彩色化过程中因近红外与可见光图像间模态差异较大,导致着色后图像在纹理细节处存在颜色晕染、区域误着色的问题,提出了颜色预测和语义感知相结合的生成对抗网络。设计颜色预测和语义感知双分支生成器,颜色预测分支采用带有跳转连接的残差网络,语义感知分支采用带有语义融合的空洞卷积金字塔结构;不同的扩张率,能够获得多个感受野提取多尺度语义特征,将感知到的语义嵌入到颜色预测分支,提高模型的语义理解能力,改善颜色晕染、区域误着色问题;设计循环一致语义损失函数,约束生成器中语义信息的一致性;算法在RGB-NIR场景数据集上进行性能实验比对以及消融实验。实验表明,所提算法相比于现有彩色化算法,PSNR、SSIM和LPIPS评价指标优于现有算法,着色效果更符合视觉感受。
彩色化 近红外图像 生成对抗网络 颜色预测 语义感知 colorization near-infrared images generative adversarial networks color prediction semantic perception
重庆大学光电技术及系统教育部重点实验室，重庆 400044
为了提高金属纳米粒子在光纤表面的富集密度，同时提高光纤表面增强拉曼散射（SERS）复合结构拉曼增强特性的稳定性，提出一种双金属（金和银）锥形光纤SERS探针结构。首先，采用化学还原法制备出形貌均一的金银纳米粒子；然后，采用光诱导的方法实现双金属在锥形光纤上的富集。制备的光纤SERS探针表现出良好的实验效果：对罗丹明6G（R6G）检测到的最低浓度低至10-10 mol/L；增强因子为2.07×108；相较于单金属银光纤SERS探针，双金属样品的稳定性提高了7倍（96 h后）。
散射 拉曼散射 双金属 锥形光纤 光诱导 光学学报
2023, 43(21): 2106003
重庆大学光电技术及系统教育部重点实验室，重庆 400044
白光干涉型法布里-珀罗（F-P）传感技术能够实现间隙值的绝对测量。本文综述了基于白光干涉的光纤F-P传感技术领域的研究工作，重点阐述了高温高压极端环境下光纤F-P传感器及其解调技术的研究现状。目的是分析高温高压环境下基于光纤F-P传感技术的物理参数测量的原理与方法，实现基于白光干涉的光纤F-P传感技术的实用化和工程化。
法布里-珀罗 白光干涉 高温高压环境 激光与光电子学进展
2023, 60(11): 1106005
1 淮阴工学院化学工程学院, 江苏省凹土资源利用重点实验室, 江苏 淮安 223003
2 淮阴工学院, 矿盐资源深度利用技术国家地方联合工程研究中心, 江苏 淮安 223003
以凹凸棒石黏土基气凝胶为精油载体制备高载量香氛剂并实现精油长效控释。以凹凸棒石为三维网络骨架、以植物纤维为增韧补强材料, 制备了一种高比表面积、高孔隙率和优良机械加工性能的的凹凸棒石/植物纤维复合气凝胶。该气凝胶对甜橙精油的负载率高达96%且挥发残油率低(<5%)。疏水改性提高了气凝胶对精油的负载率并显著延长精油缓释时间。精油挥发均呈现短暂快速下降、稳定释放、缓慢下降3段变化规律, 展示复合气凝胶对精油挥发的良好控速能力: 体积为4 cm3的香氛剂在60 ℃实验温度下可维持80 mg/h恒速释放27 h, 累计释放时间为31 h; 精油控释速率随气凝胶体积增大而增大, 在1 cm3后逐渐趋近平台值; 精油在气凝胶中的释放行为符合Korsmeyer-Peppas模型, 属于Non-Fickian扩散。
凹凸棒石 气凝胶 植物精油 缓释 palygorskite aerogel plant essential oil sustained release
1 重庆大学 微电子与通信工程学院，重庆 400044
2 四川航天电子设备研究所，成都 610100
逆光条件下弹载红外图像的密集鱼鳞波、海面亮带以及岛屿杂波严重影响了远距离红外小目标的检测性能。本文通过感知非平稳海面杂波成份存在的区域及起伏状态构建海面场景信息，采取与背景杂波相适应的信号处理方法精细检测小目标。首先，结合结构张量和Hough变换检测海天岛屿区，利用Bernaola-Galavan分割算法和方差加权信息熵表征的复杂度感知鱼鳞波、海面亮带等杂波成份，构建出海天区、平稳海区、波动海区、岛屿区的场景信息。然后，针对边缘性结构强的海天线和岛屿，提出基于方向性差异的杂波抑制算法压制杂波；在平稳海区使用顶帽变换压制杂波；在鱼鳞波、海面亮带的波动海区，提出融合灰度梯度杂波抑制算法抑制背景。最后，海天岛屿区、波动海区采用恒虚警阈值检测目标，而平稳海区采用局部峰值判决策略检测目标。相比现有先进信号检测法，实验结果表明所提方法能有效适应不同海面背景杂波，提高复杂背景下小目标检测准确性和鲁棒性。
海面背景 场景感知 杂波抑制 目标检测 小弱目标 Maritime background Scene perception Clutter suppression Target detection Small weak target 光子学报
2022, 51(12): 1210002
针对单目视觉SLAM（Simultaneous Localization and Mapping，同时定位与建图）算法无法恢复地理尺度信息、位姿估计误差累积大等问题，提出了一种基于GNSS融合的单目视觉SLAM算法。该算法基于图优化理论，在视觉里程计中构建相似变换估计模型求解真实尺度，在后端优化中加入GNSS全局地理位置节点，设计优化求解策略，提高关键帧位姿以及三维地图点位置估计的准确性，最后在序列末尾对全局地图离线迭代优化，保证地图构建的全局一致性。实验表明，在室外环境下，运动轨迹在5 km以内时，所提出方法的尺度估计误差在0.1%以内，轨迹误差在2 m以内，满足实际应用需求。
同时定位与建图 多源融合 单目视觉 尺度恢复 SLAM multi-source fusion monocular vision scale recovery
重庆大学光电技术及系统教育部重点实验室, 重庆 400044
采用了紫外光诱导的方法在二氧化钛纳米杆的表面生长银纳米粒子,将其作为表面增强拉曼散射基底。重点研究紫外光照时间对拉曼灵敏度的影响,制备不同光照时间下二氧化钛纳米杆/银复合结构的样品。利用COMSOL Multiphysics仿真软件计算二氧化钛纳米杆/银复合结构表面的电磁分布和理论增强因子。实验结果表明,紫外光照10 min后,基底对罗丹明分子的检测浓度低于10 -10 mol/L,最大增强因子约为1.84×10 8,该基底具有良好的自清洁功能。
散射 拉曼散射 可重复利用 紫外光 二氧化钛/银
