Author Affiliations
Abstract
1 Center for Terahertz Waves and School of Precision Instrument and Opto-electronics Engineering, Tianjin Universityhttps://ror.org/012tb2g32, Tianjin 300072, China
2 e-mail: lyliuma@tju.edu.cn
3 e-mail: tianzhen@tju.edu.cn
Colliding of two counter-propagating laser pulses is a widely used approach to create a laser field or intensity surge. We experimentally demonstrate broadband coherent terahertz (THz) radiation generation through the interaction of colliding laser pulses with gas plasma. The THz radiation has a dipole-like emission pattern perpendicular to the laser propagation direction with a detected peak electric field 1 order of magnitude higher than that by single pulse excitation. As a proof-of-concept demonstration, it provides a deep insight into the physical picture of laser–plasma interaction, exploits an important option to the promising plasma-based THz source, and may find more applications in THz nonlinear near-field imaging and spectroscopy.
Photonics Research
2023, 11(9): 1562
Author Affiliations
Abstract
1 Center for Terahertz Waves & School of Precision Instrument and Opto-electronics Engineering, Tianjin University, Tianjin, China
2 The Institute of Optics, University of Rochester, Rochester, USA
Ultra-broadband, intense, coherent terahertz (THz) radiation can be generated, detected, and manipulated using laser-induced gas or liquid plasma as both the THz wave transmitter and detector, with a frequency coverage spanning across and beyond the whole “THz gap.” Such a research topic is termed “plasma-based THz wave photonics in gas and liquid phases.” In this paper, we review the most important experimental and theoretical works of the topic in the non-relativistic region with pump laser intensity below .
laser-induced ionization ponderomotive force four-wave mixing asymmetric transient current model full quantum mechanical model terahertz wave generation and detection Photonics Insights
2023, 2(3): R06
Author Affiliations
Abstract
School of Physics Science and Information Engineering, Shandong Provincial Key Laboratory of Optical Communication Science and Technology, Liaocheng University, Liaocheng 252000, China
Wavelength-tunable dissipative solitons and amplifier similaritons have been obtained by inserting all-fiber Mach–Zehnder interferometer (MZI) filters with different free spectral ranges (FSRs) in a Yb-doped mode-locked fiber laser. The MZI filter is fabricated by splicing one segment of seven-core fiber (SCF) between two segments of single-mode fibers. The bandwidth of the filter depends on the FSR of the modulated interference curve and consequently depends on the tapered fiber diameter. Inserting MZI filters with bandwidths in a fiber laser and applying a tensile strain on the tapered SCF, both wavelength-tunable dissipative solitons and amplifier similaritons have been obtained.
mode-locked fiber laser dissipative soliton amplifier similaritons Mach–Zehnder interferometer Chinese Optics Letters
2023, 21(4): 041401
Author Affiliations
Abstract
1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education of China), Tianjin Universityhttps://ror.org/012tb2g32, Tianjin 300072, China
2 School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China
3 Georgia Tech Shenzhen Institute (GTSI), Tianjin University, Shenzhen 518067, China
4 e-mail: caotun1806@dlut.edu.cn
High-performance terahertz (THz) devices with reconfigurable features are highly desirable in many promising THz applications. However, most of the existing reconfigurable THz elements are still limited to volatile responses, single functionality, and time-consuming multistep manufacturing procedures. In this paper, we report a lithography-free approach to create reconfigurable and nonvolatile THz components by exploring the reversible, nonvolatile, and continuous THz modulation capability of the phase change material . As a proof of concept, THz gratings with significant Rayleigh anomalies and diffraction as well as ultrathin THz flat lenses with subwavelength and ultra-broadband focusing capabilities are designed and fabricated on ultrathin films using the presented photo-imprint strategy. Moreover, such a method can also be adopted to create more complex THz devices, such as Pancharatnam–Berry phase metasurfaces and grayscale holographic plates. With these findings, the proposed method will provide a promising solution to realize reconfigurable and nonvolatile THz elements.
Photonics Research
2023, 11(4): 669
Author Affiliations
Abstract
1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education), Tianjin University, Tianjin, China
2 Guangxi Key Laboratory of Optoelectronic Information Processing, Guilin University of Electronic Technology, Guilin, China
3 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, USA
Surface plasmons (SPs) are electromagnetic surface waves that propagate at the interface between a conductor and a dielectric. Due to their unique ability to concentrate light on two-dimensional platforms and produce very high local-field intensity, SPs have rapidly fueled a variety of fundamental advances and practical applications. In parallel, the development of metamaterials and metasurfaces has rapidly revolutionized the design concepts of traditional optical devices, fostering the exciting field of meta-optics. This review focuses on recent progress of meta-optics inspired SP devices, which are implemented by the careful design of subwavelength structures and the arrangement of their spatial distributions. Devices of general interest, including coupling devices, on-chip tailoring devices, and decoupling devices, as well as nascent SP applications empowered by sophisticated usage of meta-optics, are introduced and discussed.
surface plasmons metamaterials metasurfaces plasmonics metadevices Photonics Insights
2023, 2(1): R02
天津大学 精密仪器与光电子工程学院太赫兹研究中心 光电信息技术教育部重点实验室，天津 300072
太赫兹（THz）波由于其诸多独特的性质，有着广泛的应用前景。然而由于相关材料和器件的发展相对滞后，太赫兹技术在实际中的应用尚有诸多限制。超材料和超表面概念的提出，能够对太赫兹波的相位、振幅、偏振进行有效操控，为太赫兹技术的发展提供了许多新的思路。其重要的功能之一是依靠相位不连续将入射波反射到非镜面方向，即通称的广义斯涅尔定律。然而，此前报道的大多数异常反射装置的效率都相对较低，在实际应用中存在局限性。针对这一问题，文中提出了一种太赫兹超表面异常反射器，将法向入射光反射到 40° 方向且不改变其偏振，并从理论上阐述了提高效率的思路，且通过数值模拟展示其有效性。通过使用全介质材料构建超表面从而消除材料损耗，并利用不同布洛赫波的耦合以提供非局部响应，令器件的工作效率超过99%。此外，这一设计理念可以推广到偏振无关器件中，并且对其他类似的器件也有一定参考意义。这一工作有潜力被应用于太赫兹波激光器、太赫兹波腔谐振器等太赫兹波实际器件中。
太赫兹 超表面 异常反射 非局域性 terahertz metasurface anomalous reflection non-locality 红外与激光工程
2023, 52(2): 20220304
Author Affiliations
Abstract
1 Center for Terahertz Waves and School of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education of China), Tianjin University, Key Laboratory of Optoelectronic Information Technology (Ministry of Education of China), Tianjin 300072, China
2 School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian University of Technology, Dalian 116024, People’s Republic of China
3 Georgia Tech Shenzhen Institute (GTSI), Tianjin University, Tianjin University, Shenzhen 518067, China
Miniaturized nonvolatile reconfigurable optical components with a subwavelength thickness, extremely compact size, high-speed response, and low power consumption will be the core of next-generation all-optical integrated devices and photonic computing to replace traditional bulky optical devices and integrated circuits, which are reaching physical limitations of Moore’s law. Metasurfaces, as ultrathin planar surfaces, have played a major role in controlling the amplitude, phase, and polarization of electromagnetic waves and can be combined with various active modulation methods to realize a variety of functional devices. However, most existing reconfigurable devices are bounded in volatile nature with constant power to maintain and single functionality, which restricts their further extensive applications. Chalcogenide phase change materials (PCM) have attracted considerable attention due to their unique optical properties in the visible and infrared domains, whereas in the terahertz (THz) regime, research on the reversible phase transition in large-scale areas and applications of Ge2Sb2Te5 (GST) are still under exploration. Here, we achieved reversible, repeated, and large-area switching of GST with the help of optical and thermal stimuli. Large-area amorphization with a 1 cm diameter of GST is realized by using a single laser pulse. Then, we incorporate GST into metasurface designs to realize nonvolatile, reconfigurable, multilevel, and broadband terahertz modulators, including the anomalous deflector, metalens, and focusing optical vortex (FOV) generator. Experimental results verify the feasibility of multilevel modulation of THz waves in a broadband frequency range. Moreover, the modulators are reusable and nonvolatile. The proposed approach presents novel avenues of nonvolatile and reconfigurable metasurface designs and can enable wide potential applications in imaging, sensing, and high-speed communications.
大连理工大学 材料科学与工程学院, 辽宁省凝固控制与数字化制备技术重点实验室, 大连 116024
In2O3作为一种良好的光电和气敏材料, 因高温下具有优异的热电性能在热电领域也获得广泛关注。本研究通过固相反应法结合放电等离子烧结(SPS)成功将原位自生的InNbO4第二相引入到In2O3基体中, 优化了块体样品的制备工艺。同时, InNbO4改善了样品的电输运性能, 使载流子浓度明显提高, 在1023 K时电导率最高可达1548 S·cm-1, 高于大多数元素掺杂的样品。其中, 0.998In2O3/0.002InNbO4样品的热电性能测试表明, 在1023 K时, 其功率因子可达到0.67 mW·m-1·K-2, 热电优值(ZT)达到最高值0.187。综上所述, 通过在In2O3中原位复合InNbO4第二相可以很好地改善In2O3基热电陶瓷的电性能, 进而调控其高温热电性能。
热电材料 In2O3 InNbO4 高温热电性能 thermoelectric materials In2O3 InNbO4 thermoelectric property at high temperature 
Author Affiliations
Abstract
1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education of China), Tianjin University, Tianjin 300072, China
2 Institute of Solid State Physics, College of Physics and Electronic Science, Shanxi Province Key Laboratory of Microstructure Electromagnetic Functional Materials, Shanxi Datong University, Datong 037009, China
3 Nonlinear Physics Centre, Australian National University, Canberra, ACT 2601, Australia
4 School of Electrical and Computer Engineering, Oklahoma State University, Stillwater, Oklahoma 74078, USA
5 e-mail: cmouyang@tju.edu.cn
6 e-mail: xiaoqiang.su@sxdtdx.edu.cn
7 e-mail: weili.zhang@okstate.edu
Recent moiré configurations provide a new platform for tunable and sensitive photonic responses, as their enhanced light–matter interactions originate from the relative displacement or rotation angle in a stacking bilayer or multilayer periodic array. However, previous findings are mostly focused on atomically thin condensed matter, with limitations on the fabrication of multilayer structures and the control of rotation angles. Structured microwave moiré configurations are still difficult to realize. Here, we design a novel moiré structure, which presents unprecedented capability in the manipulation of light–matter interactions. Based on the effective medium theory and -parameter retrieval process, the rotation matrix is introduced into the dispersion relation to analyze the underlying physical mechanism, where the permittivity tensor transforms from a diagonal matrix to a fully populated one, whereas the permeability tensor evolves from a unit matrix to a diagonal one and finally becomes fully filled, so that the electromagnetic responses change drastically as a result of stacking and rotation. Besides, the experiment and simulation results reveal hybridization of eigenmodes, drastic manipulation of surface states, and magic angle properties by controlling the mutual rotation angles between two isolated layers. Here, not only a more precisely controllable bilayer hyperbolic metasurface is introduced to moiré physics, the findings also open up a new avenue to realize flat bands at arbitrary frequencies, which shows great potential in active engineering of surface waves and designing multifunctional plasmonic devices.
Photonics Research
2022, 10(9): 2056
Author Affiliations
Abstract
1 Center for Terahertz Waves and College of Precision Instrument and Optoelectronics Engineering, Key Laboratory of Optoelectronic Information Technology (Ministry of Education of China), Tianjin University, Tianjin 300072, China
2 School of Optoelectronic Engineering and Instrumentation Science, Dalian University of Technology, Dalian 116024, China
3 Georgia Tech Shenzhen Institute (GTSI), Tianjin University, Shenzhen 518067, China
4 e-mail: caotun1806@dlut.edu.cn
5 e-mail: tianzhen@tju.edu.cn
Metasurfaces, especially tunable ones, have played a major role in controlling the amplitude, phase, and polarization of electromagnetic waves and attracted growing interest, with a view toward a new generation of miniaturized devices. However, to date, most existing reconfigurable devices are bounded in volatile nature with sustained external energy to maintain and single functionality, which restrict their further applications. Here, we demonstrate for the first time, to our knowledge, nonvolatile, reconfigurable, and dynamic Janus metasurfaces by incorporating phase-change material (GST) in the terahertz (THz) regime. First, we experimentally show the reversible switching characteristic of GST on large areas by applying a single nanosecond laser pulse, which exhibits excellent contrast of THz properties in both states. Then, we present a multiplex metasurface scheme. In each metasurface, three sets of structures are adopted, in which two sets integrate GST. The effective structures can be reversely modulated by the amorphization and crystallization of GST. As a proof of concept, the dynamic beam splitter, bifocal metalens, dual-mode focusing optical vortex generators, and switchable metalens/focusing optical vortex generators are designed, fabricated, and experimentally characterized, and can be switched reversibly and repeatedly with the help of optical and thermal stimuli. Our scheme will pave the way toward the development of multifunctional and compact THz devices and may find use for applications in THz imaging, sensing, and communications.
Photonics Research
2022, 10(7): 1731
