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Color coded metadevices toward programmed terahertz switching

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Light(Science & Applications) 2024年第7期13卷 1383-1392页

作者： Weibao He xiang’ai cheng Siyang Hu Ziheng Ren Zhongyi Yu Shun Wan Yuze Hu Tian Jiang College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangshaChina. Nanhu Laser Laboratory National University of Defense TechnologyChangshaChina. Hunan Provincial Key Laboratory of High Energy Laser Technology National University of Defense TechnologyChangshaChina. Institute for Quantum Science and Technology College of ScienceNational University of Defense TechnologyChangshaChina

Terahertz modulators play a critical role in high-speed wireless communication,non-destructive imaging,and so on,which have attracted a large amount of research ***,all-optical terahertz modulation,an ultrafast dynamical control approach,remains to be limited in terms of encoding and *** we experimentally demonstrated an optical-programmed terahertz switching realized by combining optical metasurfaces with the terahertz metasurface,resulting in 2-bit dual-channel terahertz *** terahertz metasurface,made up of semiconductor islands and artificial microstructures,enables effective all-optical programming by providing multiple frequency channels with ultrafast modulation at the nanosecond ***,optical metasurfaces covered in terahertz metasurface alter the spatial light field distribution to obtain color *** to the time-domain coupled mode theory analysis,the energy dissipation modes in terahertz metasurface can be independently controlled by color excitation,which explains the principle of 2-bit encoding *** work establishes a platform for all-optical programmed terahertz metadevices and may further advance the application of composite metasurface in terahertz manipulation.

关键词： terahertz surface excitation

Optically Controlled Extraordinary Terahertz Transmission of Bi2Se3 Film Modulator

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Photonic Sensors 2019年第3期9卷 268-276页

作者： Junhu ZHOU Tong ZHOU Dongsheng YANG Zhenyu WANG Zhen ZHANG Jie YOU Zhongjie XU Xin ZHENG xiang-ai cheng College of Advanced Interdisciplinary Studies National University of Defense Technology Changsha 410073 China State Key Laboratory of High Performance Computing National University of Defense Technology Changsha 410073 China National Innovation Institute of Defense Technology Academy of Military Sciences PLA China Beijing 100010 China State Key Laboratory of Laser Interaction with Matter Northwest Insti tute of Nuclear Technology Xi'an 710024 China

Standing on the potential for high-speed modulation and switching in the terahertz (THz) regime, all-optical approaches whose response speeds mainly depend on the lifetime of nonequilibrium free carriers have attracted a tremendous attention. Here, we establish a novel bi-direction THz modulation experiment controlled by femtosecond laser for new functional devices. Specifically, time-resolved transmission measurements are conducted on a series of thin layers Bi2Se3 films fabricated straightforwardly on ai2O3 substrates, with the pump fluence range from 25(iJ/cm2 to 200 |iJ/cm2 per pulse. After photoexcitation, an ultrafast switching of THz wave with a full recovery time of ?1 Ops is observed. For a longer timescale, a photoinduced increase in the transmitted THz amplitude is found in the 8 and 10 quintuple layers (QL) BizSR, which shows a thickness-dependent topological phase transition. Additionally, the broadband modulation effect of the 8 QL Bi2Se3 film is presented at the time delays of 2.2ps and 12.5ps which have a maximum modulation depth of 6.4% and 1.3% under the pump fluence of 200(iJ/cm2, respectively. Furthermore, the absorption of a optical phonon at 1.9 THz shows a time-dependent evolution which is consistent with the cooling of lattice temperature.

关键词： Ultrafast optics topological insulator ultrafast photonic devices

Saturated absorption of different layered Bi_2Se_3 films in the resonance zone

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Photonics Research 2018年第10期6卷 I0010-I0016页

作者： JUN ZHANG TIAN JIANG TONG ZHOU HAO OUYANG CHENXI ZHANG ZHENG XIN ZHENYU WANG xiang’ai cheng College of Advanced Interdisciplinary Studies National University of Defense Technology State Key Laboratory of High Performance Computing National University of Defense Technology College of Computer National Institute of Defense Technology Innovation Academy of Military Sciences PLA China

Here, we used the micro P-scan method to investigate the saturated absorption(SA) of different layered Bi_2Se_3 continuous films. Through resonance excitation, first, we studied the influence of the second surface state(SS) on SA. The second SS resonance excitation(～2.07 e V) resulted in a free carrier cross section that was 4 orders of magnitude larger than usual. At the same time, we found that the fast relaxation process of the massless Dirac electrons is much shorter than that of electrons in bulk states. Moreover, the second SS excitation resonance reduced the saturation intensity. Second, we studied the effect of the thickness on the SA properties of *** results showed that the saturation intensity was positively correlated to the thickness, the same as the modulation depth, and the thicker the Bi_2Se_3 film was, the less the second SS would influence it. This work demonstrated that by using Bi_2Se_3 as a saturable absorber through changing the thickness or excitation wavelength, a controllable SA could be achieved.

关键词：薄膜饱和强度通讯技术发展现状

Repetition rate locked single-soliton microcomb generation via rapid frequency sweep and sideband thermal compensation

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Photonics Research 2022年第8期10卷 1859-1867页

作者： RUNLIN MIAO CHENXI ZHANG XIN ZHENG xiang’ai cheng KE YIN TIAN JIANG College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China State Key Laboratory of Pulsed Power Laser Technology Changsha 410073China Hunan Provincial Key Laboratory of High Energy Laser Technology Changsha 410073China Defense Innovation Institute Academy of Military Sciences PLA ChinaBeijing 100071China Beijing Institute for Advanced Study National University of Defense TechnologyBeijing 100000China

Dissipative Kerr solitons(DKSs)with mode-locked pulse trains in high-Q optical microresonators possess lownoise and broadband parallelized comb lines,having already found plentiful cutting-edge ***,thermal bistability and thermal noise caused by the high microresonator power and large temperature exchange between microresonator and the environment would prevent soliton microcomb formation and deteriorate the phase and frequency ***,a novel method that combines rapid frequency sweep with optical sideband thermal compensation is presented,providing a simple and reliable way to get into the single-soliton ***,it is shown that the phase and frequency noises of the generated soliton are greatly ***,by closing the locking loop,an in-loop repetition rate fractional instability of 5.5×10^(-15)at 1 s integration time and a triangular linear repetition rate sweep with 2.5 MHz could be *** demonstration provides a means for the generation,locking,and tuning of a soliton microcomb,paving the way for the application of single-soliton microcombs in low-phase-noise microwave generation and laser ranging.

关键词： resonator tuning soliton

Ultrafast all-optical terahertz modulation based on an inverse-designed metasurface

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Photonics Research 2021年第6期9卷 1099-1108页

作者： WEIBAO HE MINGYU TONG ZHONGJIE XU YUZE HU xiang’ai cheng TIAN JIANG College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China Beijing Institute for Advanced Study National University of Defense TechnologyBeijing 100020China

Metasurface plays a key role in various terahertz metadevices,while the designed terahertz metasurface still lacks flexibility and *** the other hand,inverse design has drawn plenty of attention due to its flexibility and robustness in the application of *** provides an excellent opportunity for metasurface design as well as the development of multifunctional,high-performance terahertz *** this work,we demonstrate that,for the first time,a terahertz metasurface supported by the electromagnetically induced transparency(EIT)effect can be constructed by inverse design,which combines the particle swarm optimization algorithm with the finite-difference time-domain *** germanium(Ge)film with inverse-designed metasurface,an ultrafast EIT modulation on the picosecond scale has been experimentally *** experimental results suggest a feasibility to build the terahertz EIT effect in the metasurface through an optimization algorithm of inverse ***,this method can be further utilized to design multifunctional and high-performance terahertz devices,which is hard to accomplish in a traditional metamaterial *** a word,our method not only provides a novel way to design an ultrafast all-optical terahertz modulator based on artificial metamaterials but also shows the potential applications of inverse design on the terahertz devices.

关键词： structure method inverse

Electron–phonon coupling in topological insulator Bi_2Se_3 thin films with different substrates

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Chinese Optics Letters 2019年第2期17卷 21-24页

作者： Tian Jiang Runlin Miao Jie Zhao Zhongjie Xu Tong Zhou Ke Wei Jie You Xin Zheng Zhenyu Wang xiang’ai cheng College of Advanced Interdisciplinary Studies National University of Defense Technology State Key Laboratory of High Performance Computing College of Computer National University of Defense Technology Interdisciplinary Center of Quantum Information National University of Defense Technology National Institute of Defense Technology Innovation Academy of Military Sciences PLA China

Broadband transient reflectivity traces were measured for Bi_2 Se_3 thin films with various substrates via a 400 nm pump–white-light-probe setup. We have verified the existence of a second Dirac surface state in Bi_2 Se_3 and qualitatively located it by properly analyzing the traces acquired at different probe wavelengths. Referring to the band structure of Bi_2 Se_3, the relaxation mechanisms for photo-excited electrons with different energies are also revealed and studied. Our results show a second rise of the transient reflection signal at the time scale of several picoseconds. The types of substrate can also significantly affect the dynamics of the rising signal. This phenomenon is attributed to the effect of lattice heating and coherent phonon processes. The mechanism study in this work will benefit the fabrication of high-performance photonic devices based on topological insulators.

关键词： phonon coupling insulator films

Helicity‐dependent THz emission induced by ultrafast spin photocurrent in nodal‐line semimetal candidate Mg3Bi2

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Opto-Electronic Advances 2020年第12期3卷 9-16页

作者： Mingyu Tong Yuze Hu xiangnan Xie Xiegang Zhu Zhenyu Wang xiang'ai cheng Tian Jiang College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China National Innovation Institute of Defense Technology Academy of Military Sciences PLA ChinaBeijing 100010China State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha 410073China Beijing Academy of Quantum Information Sciences Beijing 100193China Science and Technology on Surface Physics and Chemistry Laboratory Jiangyou 621908China

Helicity-dependent ultrafast spin current generated by circularly polarized photons in topological materials holds the crux to many technological improvements,such as quantum communications,on-chip communication processing and ***,we present the manipulation of helicity-dependent terahertz emission generated in a nodal line semimetal candidate Mg3Bi2 by using photon polarization *** terahertz emission is mainly ascribed to the helicity-dependent photocurrent that is originated from circular photogalvanic effects,and the helicity-independent photocurrent that is attributed to linear photogalvanic *** work will inspire more explorations into novel nodal line semimetals and open up new opportunities for developing ultrafast optoelectronics in the topological system.

关键词： terahertz spin photocurrent nodal-line semimetal topological material

Temperature insensitive multi-channel light amplification systems on SOI platform

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Chinese Optics Letters 2022年第8期20卷 29-35页

作者： Junhu Zhou Jie You Hao Ouyang Runlin Miao xiang’ai cheng Tian Jiang College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China Defense Innovation Institute Academy of Military Sciences PLA ChinaBeijing 100071China Beijing Institute for Advanced Study National University of Defense TechnologyBeijing 100020China

We present a theoretical analysis of a novel multi-channel light amplification photonic system on chip,where the nonlinear Raman amplification phenomenon in the silicon(Si)wire waveguide is ***,a compact and temperature insensitive Mach–Zehnder interferometer filter working as demultiplexer is also exploited,allowing for the whole Si photonic system to be free from thermal *** propagation of the multi-channel pump and Stokes lights is described by a rigorous theoretical model that incorporates all relevant linear and nonlinear optical effects,including the intrinsic waveguide optical losses,first-and second-order frequency dispersion,self-phase and cross-phase modulation,phase shift and two-photon absorption,free-carriers dynamics,as well as the inter-pulse Raman ***,to prevent excessive drift of the transmission window of the demultiplexer caused by ambient temperature variations and high thermo-optical coefficient of Si,an asymmetric waveguide width is adopted in the upper and lower arms of each Mach–Zehnder interferometer lattice cell.A Chebyshev half-band filter is utilized to achieve a flat pass-band transmission,achieving a temperature sensitivity of<1.4 pm=K and over 100 K temperature *** all-Si amplifier shows a thermally robust behavior,which is desired by future Si-on-insulator(SOI)applications.

关键词： silicon-on-insulator multi-channel amplification temperature

Ultrasensitive polarization-dependent terahertz modulation in hybrid perovskites plasmoninduced transparency devices

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Photonics Research 2019年第9期7卷 994-1002页

作者： JUNHU ZHOU YUZE HU TIAN JIANG HAO OUYANG HAN LI YIZHEN SUI HAO HAO JIE YOU XIN ZHENG ZHONGJIE XU xiang’ai cheng College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha410073China State Key Laboratory of High Performance Computing College of ComputerNational University of Defense TechnologyChangsha410073China National Innovation Institute of Defense Technology Academy of Military Sciences PLA ChinaBeijing100071China

Active control of metamaterial properties with high tunability of both resonant intensity and frequency is essential for advanced terahertz(THz) applications, ranging from spectroscopy and sensing to *** varied metamaterials, plasmon-induced transparency(PIT) has enabled active control with giant sensitivity by embedding semiconducting materials. However, there is still a stringent challenge to achieve dynamic responses in both intensity and frequency modulation. Here, an anisotropic THz active metamaterial device with an ultrasensitive modulation feature is proposed and experimentally studied. A radiative-radiative-coupled PIT system is established, with a frequency shift of 0.26 THz in its sharp transparent windows by polarization rotation. Enabled by high charge-carrier mobility and longer diffusion lengths, we utilize a straightforwardly spincoated MAPbI3 film acting as a photoactive medium to endow the device with high sensitivity and ultrafast *** the device is pumped by an ultralow laser fluence, the PIT transmission windows at 0.86 and 1.12 THz demonstrate a significant reduction for two polarizations, respectively, with a full recovery time of 561 ps. In addition, we numerically prove the validity that the investigated resonator structure is sensitive to the optically induced conductivity. The hybrid system not only achieves resonant intensity and frequency modulations simultaneously, but also preserves the all-optical-induced switching merits with high sensitivity and speed, which enriches multifunctional subwavelength metamaterial devices at THz frequencies.

关键词： THz Ultrasensitive polarization-dependent terahertz modulation in hybrid perovskites plasmoninduced transparency devices