1 复旦大学物理学系,应用表面物理国家重点实验室,上海市超构表面光场调控重点实验室,上海 200433
2 复旦大学光科学与工程系上海超精密光学制造工程技术研究中心,上海 200433
从超构表面调控电磁波研究的发展历史出发,详细介绍了基于复合相位超构表面实现高效多功能调控圆偏振电磁波的原理、设计思路和实验模拟表征,对近期国内外在这一领域的研究进展进行简要的论述,着力以此引导相关研究性实验教学,并为相关领域研究人员提供指引。
超构表面 共振相位 传输相位 几何相位 复合相位 圆偏振光 多功能 光学学报
2024, 44(10): 1026008
1 湖南科技大学 难加工材料高效精密加工湖南省重点实验室,湘潭 411201
2 湖南科技大学 机电工程学院,湘潭 411201
3 上汽大众汽车有限公司长沙分公司,长沙 410000
激光增材制造过程的工艺参数直接影响成型件的成形质量及性能,对工艺参数的优化是实现成形质量调控的最有效方法。建立准确、高精度的工艺参数与成形质量之间的模型,对于成形质量的预测及工艺参数的优选极其重要。对激光增材制造工艺参数优化建模的方法进行了总结和综述,且对工艺系统开发进行了现状分析,论述了工艺优化建模方法的原理以及优缺点,最后对激光增材制造工艺优化建模研究前景进行了展望。
激光技术 优化建模 工艺参数 工艺系统 增材制造 laser technique optimization model process parameters process system additive manufacturing
1 北方信息控制研究院集团有限公司,江苏南京 210000
2 驻南京地区第三军事代表室,江苏南京 210000
针对跨海桥梁或沿海机场等场所需要实时测算获取移动船只目标绝对位置和高程的现实需要,文中介绍一种高精度光电船只目标定位系统设计与实现方案。通过将高清高精度光学探测组件集成于高精度云台设备内部,可实时解算出目标点的绝对位置信息和高程信息并上报监控系统。结合雷达系统引导可实现无人值守情况下自动测算过往船只经纬度坐标及高程功能。经实际运行测试,该系统展现出良好的可靠性,具有较好的测量精度和应用前景。
光学探测组件 云台 无人值守 自动测算 经纬度坐标 高程 optical detection assembly, PTZ, unattended, autom
Author Affiliations
Abstract
1 Fudan University, State Key Laboratory of Surface Physics, Department of Physics, Shanghai, China
2 Fudan University, Key Laboratory of Micro and Nano Photonic Structures, Shanghai, China
3 Shanghai Research Center for Quantum Sciences, Shanghai, China
4 Beijing Normal University, Center for Advanced Quantum Studies, Department of Physics, Beijing, China
5 Fudan University, Institute for Nanoelectronic Devices and Quantum Computing, Shanghai, China
Precise and ultrafast control over photo-induced charge currents across nanoscale interfaces could lead to important applications in energy harvesting, ultrafast electronics, and coherent terahertz sources. Recent studies have shown that several relativistic mechanisms, including inverse spin-Hall effect, inverse Rashba–Edelstein effect, and inverse spin-orbit-torque effect, can convert longitudinally injected spin-polarized currents from magnetic materials to transverse charge currents, thereby harnessing these currents for terahertz generation. However, these mechanisms typically require external magnetic fields and exhibit limitations in terms of spin-polarization rates and efficiencies of relativistic spin-to-charge conversion. We present a nonrelativistic and nonmagnetic mechanism that directly utilizes the photoexcited high-density charge currents across the interface. We demonstrate that the electrical anisotropy of conductive oxides RuO2 and IrO2 can effectively deflect injected charge currents to the transverse direction, resulting in efficient and broadband terahertz radiation. Importantly, this mechanism has the potential to offer much higher conversion efficiency compared to previous methods, as conductive materials with large electrical anisotropy are readily available, whereas further increasing the spin-Hall angle of heavy-metal materials would be challenging. Our findings offer exciting possibilities for directly utilizing these photoexcited high-density currents across metallic interfaces for ultrafast electronics and terahertz spectroscopy.
terahertz optics ultrafast science nanophotonics Advanced Photonics
2023, 5(5): 056006
强激光与粒子束
2023, 35(7): 071003
Author Affiliations
Abstract
1 State Key Laboratory of Surface Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and Department of Physics, Fudan University, 200433 Shanghai, People’s Republic of China
2 Academy for Engineering and Technology, Fudan University, 200433 Shanghai, People’s Republic of China
3 Collaborative Innovation Center of Advanced Microstructures, 210093, Nanjing, People’s Republic of China
Freely switching light transmission and absorption via an achromatic reflectionless screen is highly desired for many photonic applications (e.g., energy-harvesting, cloaking, etc.), but available meta-devices often exhibit reflections out of their narrow working bands. Here, we rigorously demonstrate that an optical metasurface formed by two resonator arrays coupled vertically can be perfectly reflectionless at all frequencies below the first diffraction mode, when the near-field (NF) and far-field (FF) couplings between two constitutional resonators satisfy certain conditions. Tuning intrinsic loss of the system can further modulate the ratio between light transmission and absorption, yet keeping reflection diminished strictly. Designing/fabricating a series of metasurfaces with different inter-resonator configurations, we experimentally illustrate how varying inter-resonator NF and FF couplings can drive the system to transit between different phase regions in a generic phase diagram. In particular, we experimentally demonstrate that a realistic metasurface satisfying the discovered criteria exhibits the desired achromatic reflectionless property within 160–220 THz (0–225 THz in simulation), yet behaving as a perfect absorber at ~ 203 THz. Our findings pave the road to realize meta-devices exhibiting designable transmission/absorption spectra immune from reflections, which may find many applications in practice.
Author Affiliations
Abstract
Fudan University, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education) and Department of Physics, State Key Laboratory of Surface Physics, Shanghai, China
Dynamically controlling terahertz (THz) waves with an ultracompact device is highly desired, but previously realized tunable devices are bulky in size and/or exhibit limited light-tuning functionalities. Here, we experimentally demonstrate dynamic modulation on THz waves with a dielectric metasurface in mode-selective or mode-unselective manners through pumping the system at different optical wavelengths. Quasi-normal-mode theory reveals that the physics is governed by the spatial overlap between wave functions of resonant modes and regions inside resonators perturbed by pump laser excitation at different wavelengths. We further design/fabricate a dielectric metasurface and experimentally demonstrate that it can dynamically control the polarization state of incident THz waves, dictated by the strength and wavelength of the pumping light. We finally numerically demonstrate pump wavelength-controlled optical information encryption based on a carefully designed dielectric metasurface. Our studies reveal that pump light wavelength can be a new external knob to dynamically control THz waves, which may inspire many tunable metadevices with diversified functionalities.
dynamic metasurfaces terahertz quasi-normal-mode theory optical pumping Advanced Photonics
2023, 5(2): 026005
1 西南交通大学材料科学与工程学院,四川 成都 610031
2 成都交大智辉激光科技有限公司,四川 彭州611936
采用纳秒脉冲激光器对TC4钛合金表面的氧化膜及油污进行激光清洗,研究了扫描速度对清洗后试样表面形貌、成分、元素含量及价态的影响规律,并分析了扫描速度对表面粗糙度、硬度和耐腐蚀性能的影响。结果表明:当扫描速度为500 mm/s时,激光对基体的损伤大且会发生热氧化,表面形成TiO,O含量较高。随着扫描速度由3000 mm/s增加至10000 mm/s,表面逐渐变得光滑平整,O含量先降低后升高,Ti含量则先升高后降低。当扫描速度为9000 mm/s时,表面Ti含量(质量分数)达到最大值84.24%,O含量(质量分数)降至最小值4.54%,且粗糙度(Ra)最低约为0.907 μm,清洗效果最佳。扫描速度的增加使清洗后表面的粗糙度先升高后降低。此外,激光清洗可使TC4钛合金表面的硬度和耐腐蚀性能有所提高。
激光技术 激光清洗 钛合金氧化膜 表面形貌 化学成分 粗糙度 电化学腐蚀
Author Affiliations
Abstract
1 State Key Laboratory of Surface Physics and Department of Physics, Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Fudan University, Shanghai 200433, China
2 Shanghai Engineering Research Centre of Ultra-Precision Optical Manufacturing, Green Photonics and Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China
Metasurfaces have exhibited great capabilities to control electromagnetic waves, and many multifunctional metasurfaces were recently proposed. However, although angle-multiplexed meta-devices were successfully realized in reflection geometries, their transmission-mode counterparts are difficult to achieve due to the additional requirements. Here, we design and fabricate a transmissive angle-multiplexed meta-polarizer in the microwave regime based on a multilayer metasurface. Coupled-mode-theory analyses reveal that the device exhibits distinct angle-dependent transmissive responses under excitations with different polarizations, and such differences are further enhanced by multiple scatterings inside the device. Microwave experimental results are in good agreement with numerical simulations and theoretical analyses.
metasurfaces angular dispersion multifunctional meta-device polarization modulation Chinese Optics Letters
2023, 21(2): 023603