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Quantitative analysis of the self-absorption and reemission effects on the emission spectrum of photoluminescence in right-angle excitation–detection configuration

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Chinese Physics B 2013年第11期22卷 268-274页

作者：王振华吴玉娥张心正云志强李威许京军 The key laboratory of weak-light nonlinear photonics Ministry of Education TEDA Applied Physics School and School of Physics Nankai University

A theoretical approach based on differential radiative transport is proposed to quantitatively analyze the self- absorption and reemission effects on the emission spectrum for right angle excitation-detection photoluminescence mea- surements, and the wavelength dependence of the reemission effect is taken into account. Simulations and experiments are performed using rhodamine 6G solutions in ethanol as model samples. It is shown that the self-absorption effect is the dominant effect on the detected spectrum by inducing pseudo red-shift and reducing total intensity; whereas the reemission effect partly compensates for signal decrease and also results in an apparent signal gain at the wavelengths without ab- sorption. Both effects decrease with the decrease in the sample concentration and the propagation distance of the emission light inside the sample. We therefore suggest that diluted solutions are required for accurate photoluminescence spectrum measurements and photoluminescence-based measurements.

关键词： photoluminescence self-absorption effect reemission effect radiative transport

Topologically tuned terahertz confinement in a nonlinear photonic chip

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light(Science & Applications) 2022年第6期11卷 1296-1303页

作者： Jiayi Wang Shiqi Xia Ride Wang Ruobin Ma Yao Lu Xinzheng Zhang Daohong Song Qiang Wu Roberto Morandotti Jingjun Xu Zhigang Chen The moe key laboratory of weak-light nonlinear photonics TEDA Institute of Applied Physics and School of PhysicsNankai UniversityTianjin 300457China Innovation laboratory of Terahertz Biophysics National Innovation Institute of Defense Technology100071 BeijingChina Collaborative Innovation Center of Extreme Optics Shanxi University030006 TaiyuanShanxiChina INRS-EMT 1650 Blvd.Lionel-BouletVarennesQC J3X 152Canada

Compact terahertz(THz)functional devices are greatly sought after for high-speed wireless communication,biochemical sensing,and non-destructive ***,controlled THz generation,along with transport and detection,has remained a challenge especially for chip-scale devices due to low-coupling efficiency and unavoidable absorption ***,based on the topological protection of electromagnetic waves,we demonstrate nonlinear generation and topologically tuned confinement of THz waves in an engineered lithium niobate chip forming a wedge-shaped Su-Schrieffer-Heeger *** measured band structures provide direct visualization of the THz localization in the momentum space,while robustness of the confined mode against chiral perturbations is also analyzed and compared for both topologically trivial and nontrivial *** topological control of THz waves may bring about new possibilities in the realization of THz integrated circuits,promising for advanced photonic applications.

关键词： nonlinear realization wedge

Highly Directional Emission from a Subwavelength Slit in Metal-Dielectric Layered Films

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Chinese Physics Letters 2006年第5期23卷 1207-1210页

作者：李祖斌田建国周文远刘智波臧维平张春平 The moe key Lab of Advanced Technique & Fabrication for weak-light nonlinear photonics Materials and Tianjin Key Lab of Photonics Materials & Technology for Information Science Nankai University Tianjin 300457

The directional light emission from a single subwavelength slit surrounded by periodic grooves in layered films consisting of Ag and transparent dielectric is analysed numerically by the finite difference time domain method. The results show that the transmission through this structure is strongly confined by the modulation of the dielectric film with grooves on the output side. The role of evanescent waves in this phenomenon is discussed. It is the re-diffraction of the evanescent waves （that are generated by the diffraction of the subwavelength slit） caused by the grooves on the dielectric film that leads to the directional transmission. Some suggestions are given to obtain beaming light with high transmittance.

关键词： ENHANCED MICROWAVE TRANSMISSION APERTURE RADIATION light

Enhanced Fano resonance for high-sensitivity sensing based on bound states in the continuum

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Chinese Optics Letters 2023年第3期21卷 54-59页

作者：冯光陈智辉王扬刘欣刘寅山刘啸孙非杨毅彪陈树琪 key laboratory of Advanced Transducers and Intelligent Control System Ministry of Education and Shanxi ProvinceCollege of Physics and OptoelectronicsTaiyuan University of TechnologyTaiyuan 030024China key laboratory of Chemical Biology and Molecular Engineering Ministry of EducationInstitute of BiotechnologyShanxi UniversityTaiyuan 030006China key laboratory of weak light nonlinear photonics Ministry of EducationRenewable Energy Conversion and Storage CenterSchool of Physics and TEDA Institute of Applied PhysicsNankai UniversityTianjin 300071China

Although previously reported terahertz absorbers can achieve high-sensitivity refractive index sensing,the resonant peak is too broad,which leads to a low figure of merit[FOM].Transmissive sensors based on bound states in the continuum[BIC]can achieve high FOM,but they have some limitations in high ***,we propose a periodic triple parallel metal bars structure to obtain high quality,a strong field,and multiple hot spots by the Friedrich-Wintgen *** results show the sensitivity and FOM can reach 1877 GHz/RIU and 665,*** to the previously reported transmissive sensors based on BIC,the sensitivity has been greatly improved.

关键词： Fano resonance bound states in the continuum terahertz high-sensitivity sensing

Dynamically taming focal fields of femtosecond lasers for fabricating microstructures

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Chinese Optics Letters 2022年第1期20卷 6-11页

作者：蔡孟强王强涂成厚李勇男王慧田 School of Physics and key laboratory of weak light nonlinear photonics Nankai UniversityTianjin 300071China Institute of Space Science and Technology Nanchang UniversityNanchang 330031China National laboratory of Solid State Microstructures Nanjing UniversityNanjing 210093China Collaborative Innovation Center of Advanced Microstructures Nanjing UniversityNanjing 210093China Collaborative Innovation Center of light Manipulations and Applications Shandong Normal UniversityJinan 250358China

Micromachining based on femtosecond lasers usually requires accurate control of the sample movement,which may be very complex and ***,the exploration of micromachining without sample movement is ***,we have illustrated the manipulation of optical fields by controlling the polarization or phase to vary periodically and then realized certain focal traces by real-time loading of the computer-generated holograms(CGHs) on the spatial light *** focal trace is composed of many discrete focal spots,which are generated experimentally by using the real-time dynamically controlled *** the designed focal traces,various microstructures such as an ellipse,a Chinese character "Nan",and an irregular quadrilateral grid structure are fabricated in the z-cut LiNbO_(3) wafers,showing good qualities in terms of continuity and *** method proposes a movement free solution for micromachining samples and completely abandons the high precision stage and complex movement control,making microstructure fabrication more flexible,stable,and cheaper.

关键词： manipulation of optical fields computer-generated holograms focal trace microstructures

Interfaces of high-efficiency kesterite Cu_2ZnSnS(e)_4 thin film solar cells

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Chinese Physics B 2018年第1期27卷 2-18页

作者：高守帅姜振武武莉敖建平曾玉孙云张毅 Institute of Photoelectronic Thin Film Devices and Technology Tianjin Key Laboratory of Photoelectronic Thin Film Devices and TechnologyNankai University The moe key laboratory of weak-light nonlinear photonics School of Physics Nankai University

Cu2ZnSnS（e）4 （CZTS（e）） solar cells have attracted much attention due to the elemental abundance and the non- toxicity. However, the record efficiency of 12.6% for CuzZnSn（S,Se）4 （CZTSSe） solar cells is much lower than that of Cu（In,Ga）See （CIGS） solar cells. One crucial reason is the recombination at interfaces. In recent years, large amount inves- tigations have been done to analyze the interfacial problems and improve the interfacial properties via a variety of methods. This paper gives a review of progresses on interfaces of CZTS（e） solar cells, including：（i） the band alignment optimization at buffer/CZTS（e） interface, （ii） tailoring the thickness of MoS（e）2 interfacial layers between CZTS（e） absorber and Mo back contact, （iii） the passivation of rear interface, （iv） the passivation of front interface, and （v） the etching of secondary phases.

关键词： Cu2ZnSnS4 solar cells kesterite interface passivation

Symmetry-protected third-order exceptional points in staggered flatband rhombic lattices

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photonics Research 2023年第2期11卷 225-233页

作者： YINGYING ZHANG SHIQIANG XIA XINGDONG ZHAO LU QIN XUEJING FENG WENRONG QI YAJING JIANG HAI LU DAOHONG SONG LIQIN TANG ZUNLUE ZHU WUMING LIU YUFANG LIU School of Physics Henan Normal UniversityXinxiang 453007China moe key laboratory of weak-light nonlinear photonics TEDA Applied Physics Institute and School of PhysicsNankai UniversityTianjin 300457China Beijing National laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China Institute of Physics Henan Academy of SciencesZhengzhou 450046China

Higher-order exceptional points(EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still remains a challenge due to the strict requirement of the system symmetries. Here we demonstrate that higher-order EPs can be judiciously fabricated in parity–time(PT)-symmetric staggered rhombic lattices by introducing not only on-site gain/loss but also non-Hermitian couplings. Zero-energy flatbands persist and symmetry-protected third-order EPs(EP3s) arise in these systems owing to the non-Hermitian chiral/sublattice symmetry, but distinct phase transitions and propagation dynamics occur. Specifically, the EP3 arises at the Brillouin zone(BZ) boundary in the presence of on-site gain/loss. The single-site excitations display an exponential power increase in the PT-broken phase. Meanwhile, a nearly flatband sustains when a small lattice perturbation is applied. For the lattices with non-Hermitian couplings, however, the EP3 appears at the BZ center. Quite remarkably, our analysis unveils a dynamical delocalization-localization transition for the excitation of the dispersive bands and a quartic power increase beyond the EP3. Our scheme provides a new platform toward the investigation of the higher-order EPs and can be further extended to the study of topological phase transitions or nonlinear processes associated with higher-order EPs.

关键词： exceptional protected symmetry

Mode characteristics of silver-coated inverted-wedge silica microdisks

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Science China(Physics,Mechanics & Astronomy) 2015年第11期58卷 40-44页

作者： BO Fang WANG XiaoOu LI Ying GAO Feng ZHANG GuoQuan XU JingJun The key laboratory of weak-light nonlinear photonics Ministry of Education TEDA Applied Physics Institute and School of PhysicsNankai University

The characteristics of whispering gallery modes(WGM) in silver-coated inverted-wedge silica microdisks are theoretically investigated by using finite element method. Dielectric TE mode always exists in silver-coated inverted-wedge resonators; dielectric TM mode tends to couple with SPP modes; only pure interior surface plasmonic polariton(SPP) mode but not pure exterior SPP mode is observed in contrast to the metal-coated cylindrical and toroidal resonators. The dependence of quality factor of different kinds of WGMs on the radius of the resonator and the thickness of the coated silver layer are systematically analyzed. We find that the quality factors of the hybrid WGMs associated with SPP mode can reach 104. The maximum light intensity enhancement in ambient for a hybrid mode consisting of a dielectric TM mode and an exterior SPP mode can be obtained when a silver film of thickness ~40 nm is deposited. The silver-coated inverted-wedge silica resonators may be widely applied in sensing and surface enhanced Raman scattering.

关键词：科学学科学知识物理学力学天文学

Fabrication of magneto-optical microstructure by femtosecond laser pulses

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Chinese Optics Letters 2012年第10期10卷 68-70页

作者：李玉栋郜向阳姜美玲孙骞田建国 key laboratory of weak light nonlinear photonics Ministry of EducationSchool of Physics and TEDA Applied Physics SchoolNankai University

We investigate femtosecond laser direct writing （FLDW） in the fabrication of magneto-optical （MO） microstructures. The experimental results show that FDLW can introduce positive refractive index change in the MO materials. With the increase of the writing intensity of femtosecond laser pulses, refractive index change increases, whereas Verdet constant of the damaged area decreases nonlinearly. With suitable writing intensity, we obtain a single-mode waveguide in which Verdet constant is 80% of the bulk MO glass.

关键词： Microstructure Optical waveguides Ultrafast lasers