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Chinese Physics B 2013年第3期22卷 44-49页

作者：叶佳声王进泽黄庆礼董碧珍张岩杨国桢 Department of Physics Capital Normal University beijing key laboratory for thz spectroscopy and imaging Key Laboratory of THz OptoelectronicsMinistry of Education Institute of Physics Chinese Academy of Sciences

In this paper,a novel method is proposed and employed to design a single diffractive optical element（DOE） for implementing spectrum-splitting and beam-concentration（SSBC） functions *** develop an optimization algorithm,through which the SSBC DOE can be optimized within an arbitrary thickness range according to the limitations of modern photolithography *** simulation results reveal that the designed SSBC DOE has a high optical focusing *** is expected that the designed SSBC DOE should have practical applications in high-efficiency solar cell systems.

关键词： diffractive optical element spectrum-splitting and beam-concentration functions thickness optimization algorithm solar cell systems

Broadband and high efficiency terahertz metasurfaces for anomalous refraction and vortex beam generation

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Chinese Physics B 2022年第10期31卷 583-591页

作者： Wen-Yu Li Ran Sun Jing-Yu Liu Tian-Hua Meng Guo-Zhong Zhao Department of Physics Capital Normal UniversityBeijing Key Laboratory for THz Spectroscopy and ImagingKey Laboratory of THz OptoelectronicsMinistry of EducationBeijing 100048China Institute of Solid State Physics Shanxi Datong UniversityDatong 037009China

The applications of metasurfaces are currently a highly active research field due to their extraordinary ability to manipulate electromagnetic waves. The ultra-thin characteristics of metasurfaces allow the miniaturization and integration of metasurface devices. However, these devices work typically under a low efficiency and narrow bandwidth condition. In this work, we design eight multilayered unit cells with similar amplitudes and a phase interval of π/4, which convert the polarization states of the terahertz(thz) waves between two orthogonal directions. The average cross-polarized transmission amplitudes of these cells are all around 0.9 in an ultra-broad frequency range from 0.5 thz to 1.4 thz. Furthermore,unit cells are used to construct both an ultra-thin anomalous refraction metalens and a vortex phase plate. Our simulation results show that the anomalous refraction for the transmitted linear polarization component is comparable to the theoretical prediction, and the maximum error is determined to be below 4.8%. The vortex phase plate can also generate an ideal terahertz vortex beam with a mode purity of 90% and more. The distributions of longitudinal electric field, intensity, and phase illustrate that the generated vortex beam has excellent propagation characteristics and a weak divergence. Simulations of the two types of metasurface devices, based on the eight unit cells, exhibit very high efficiencies in a wide bandwidth. Our research will assist in the improvement in the practical applications of metasurfaces. It also provides a reference for the design of high efficiency and broadband devices that are applied to other frequency ranges.

关键词： terahertz metasurface anomalous refraction vortex beam generation

High efficiency and broad bandwidth terahertz vortex beam generation based on ultra-thin transmission Pancharatnam-Berry metasurfaces

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Chinese Physics B 2021年第5期30卷 667-672页

作者： Wenyu Li Guozhong Zhao Tianhua Meng Ran Sun Jiaoyan Guo Department of Physics Capital Normal UniversityBeijing Key Laboratory for THz Spectroscopy and ImagingKey Laboratory of THz OptoelectronicsMinistry of EducationBeijing 100048China Institute of Solid State Physics Shanxi Datong UniversityDatong 037009China

The terahertz(thz)vortex beam generators are designed and theoretically investigated based on single-layer ultra-thin transmission *** phase changes of metasurfaces are obtained by utilizing Pancharatnam-Berry phase elements,which possess different rotation angles and are arranged on two concentric rings centered on the *** circularly polarized incident thz beam could be turned into a cross-polarization transmission wave,and the orbital angular momentum(OAM)varies in value by *** l values change from±1 to±5,and the maximal cross-polarization conversion efficiency that could be achieved is 23%,which nearly reaches the theoretical limit of a single-layer *** frequency range of the designed vortex generator is from 1.2 thz to 1.9 thz,and the generated thz vortex beam could keep a high fidelity in the operating *** propagation behavior of the emerged thz vortex beam is analyzed in *** work offers a novel way of designing ultra-thin and single-layer vortex beam generators,which have low process complexity,high conversion efficiency and broad bandwidth.

关键词： metasurface terahertz vortex beam Pancharatnam-Berry phase element conversion efficiency

thz spectra of parabens at low temperature

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Science China(Information Sciences) 2012年第1期55卷 114-119页

作者： ZHAO GuoZhong,WANG He,LIU LiMing&WANG XiaoYan Department of Physics,Capital Normal University,beijing key Lab for thz spectroscopy and imaging,key Lab of thz Optoelectronics,Ministry of Education,beijing 100048,China Department of Physics Capital Normal University Beijing Key Lab for THz Spectroscopy and Imaging Key Lab of THz Optoelectronics Ministry of Education Beijing China

Terahertz transmission spectra of methylparaben,ethylparaben,propyl-p-hydroxybenzoate and butyl-p-hydroxybenzoate were measured by terahertz time-domain spectroscopy(thz-TDS)at 7.8 *** it was dicult to observe the thz absorbance peaks of these esters at room temperature(294.3 K),they could be observed at 7.8 *** thz absorbance peaks of these materials were at a higher frequency at 7.8 K than that at room *** functional theory(DFT) was used to simulate the vibrational spectrum of ethylparaben to study the origin of the thz absorbance *** research provides reference data for the spectral properties of parabens and the identification of their molecular structures and vibration modes in the terahertz range.

关键词： terahertz spectroscopy low temperature parabens

Design optimization of highly efficient spectrum-splitting and beam-concentrating diffractive optical element for lateral multijunction solar cells

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Chinese Physics B 2014年第4期23卷 319-323页

作者：王进泽叶佳声黄庆礼许信李冬梅孟庆波杨国桢 key laboratory for Renewable Energy CAS) Institute of Physics Chinese Academy of Sciences beijing key laboratory for New Energy Materials and Devices Institute of Physics Chinese Academy of Sciences Department of Physics Capital Normal University beijing key laboratory for thz spectroscopy and imaging Key Laboratory of THz Optoelectronics Ministry of Education laboratory of Optical Physics Chinese Academy of Sciences

Two improved algorithms are proposed to extend a diffractive optical element （DOE） to work under the broad spec- trum of sunlight. An optimum design has been found for the DOE, with a weighted average optical efficiency of about 6.8% better than that of the previous design. The optimization of designing high optical efficiency DOEs will pave the way for future designs of high-efficiency, low-cost lateral multijunction solar cells based on such a DOE.

关键词： thickness optimization solar cell split concentration diffractive optical element

Realizing high photovoltaic efficiency with parallel multijunction solar cells based on spectrum-splitting and-concentrating diffractive optical element

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Chinese Physics B 2015年第5期24卷 329-334页

作者：王进泽黄庆礼许信全宝钢罗建恒张岩叶佳声李冬梅孟庆波杨国桢 beijing National laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences key laboratory for Renewable Energy Institute of Physics Chinese Academy of Sciences beijing key laboratory for New Energy Materials and Devices Institute of Physics Chinese Academy of Sciences laboratory of Microfabrication Institute of Physics Chinese Academy of Sciences beijing key laboratory for thz spectroscopy and imaging Key Laboratory of THz Optoelectronics Ministry of Education laboratory of Optical Physics Institute of Physics Chinese Academy of Sciences

Based on the facts that multijunction solar cells can increase the efficiency and concentration can reduce the cost dramatically, a special design of parallel multijunction solar cells was presented. The design employed a diffractive optical element （DOE） to split and concentrate the sunlight. A rainbow region and a zero-order diffraction region were generated on the output plane where solar cells with corresponding band gaps were placed. An analytical expression of the light intensity distribution on the output plane of the special DOE was deduced, and the limiting photovoltaic efficiency of such parallel multijunction solar ceils was obtained based on Shockley-Queisser＇s theory. An efficiency exceeding the Shockley--Queisser limit （33%） can be expected using multijunction solar cells consisting of separately fabricated subcells. The results provide an important alternative approach to realize high photovoltaic efficiency without the need for expensive epitaxial technology widely used in tandem solar cells, thus stimulating the research and application of high efficiency and low cost solar cells.

关键词： diffractive optical element split concentration multijunction

Diffraction of terahertz waves after passing through a Fresnel lens

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Chinese Physics B 2009年第12期18卷 5511-5517页

作者：施宇蕾周庆莉张存林 beijing key laboratory for Terahertz spectroscopy and imaging Key Laboratory of Terahertz OptoelectronicsMinistry of EducationDepartment of PhysicsCapital Normal University

The spatiotemporal and spectral characteristics of ultrawide-band terahertz pulses after passing through a Fresnel lens are studied by using the scalar diffraction theory. The simulation shows that the transmitted terahertz waveforms compress with increasing propagation distance, and the multi-frequency focusing phenomenon at different focal points is observed. Additionally, the distribution of terahertz fields in a plane perpendicular to the axis is also discussed, and it is found that the diffraction not only induces focusing on-axis but also inhibits focusing at off-axis positions. Therefore, the Fresnel lens may be a useful alternative approach to being a terahertz filter. Moreover, the terahertz pulses travelling as a basic mode of a Gaussian beam are discussed in detail.

关键词： terahertz Fresnel lens diffraction field

Transient surface photoconductivity of GaAs emitter studied by terahertz pump-emission spectroscopy

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Chinese Physics B 2009年第10期18卷 4515-4520页

作者：施宇蕾周庆莉张存林 beijing key laboratory for Terahertz spectroscopy and imaging Key Laboratory of Terahertz Optoelectronics Ministry of Education Department of Physics Capital Normal University

This paper investigates the ultrafast carrier dynamics and surface photoconductivity of unbiased semi-insulating GaAs in detail by using a terahertz pump-emission technique. Based on theoretical modelling, it finds that transient photoconductivity plays a very important role in the temporal waveform of terahertz radiation pulse. Anomalous enhancement in both terahertz radiation and transient photoconductivity is observed after the excitation of pump pulse and we attribute these phenomena to carrier capture in the EL2 centers. Moreover, the pump power- and temperature- dependent measurements are also performed to verify this trapping model.

关键词： terahertz ultrafast carrier trapping surface photoconductivity

Transient optical modulation properties in the terahertz metamaterial of split ring resonators

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Chinese Physics B 2012年第5期21卷 692-696页

作者：周庆莉施宇蕾王爱华李磊张存林 beijing key laboratory for Terahertz spectroscopy and imaging Key Laboratory of Terahertz Optoelectronics of Ministry of EducationDepartment of PhysicsCapital Normal University

The ultrafast optical modulation properties of split ring resonators are characterized by utilizing optical pump-terahertz probe *** experimental results show that when the terahertz electric vector is perpendicular to the gap of the split ring resonator,resonant absorption can be quenched significantly under high pump ***,when the terahertz electric vector is parallel to the gap,the resonant absorption is less sensitive to pump excitation due to the structural properties of the *** numerical simulations also demonstrate that the pump pulse significantly influences the split ring resonator current by generating carriers in the substrate.

关键词： terahertz carrier dynamics ultrafast spectra

Anomalous behaviours of terahertz reflected waves transmitted from GaAs induced by optical pumping

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Chinese Physics B 2009年第12期18卷 5518-5522页

作者：施宇蕾周庆莉赵冬梅张存林 beijing key laboratory for Terahertz spectroscopy and imaging Key Laboratory of Terahertz OptoelectronicsMinistry of EducationDepartment of PhysicsCapital Normal University

Femtosecond pump-terahertz probe studies of carrier dynamics in semi-insulating CaAs have been investigated in detail for various pump powers. It is observed that, at high pump powers, the reflection peaks flip to the opposite polarity and dramatically enhance as the pump arrival time approaches the reflected wave of the terahertz pulse. The abnormal polarity-flip and enhancement can be interpreted by the pump-induced enhancement in the photoconductivity of GaAs and half-wave loss. Moreover, the carrier relaxation processes and surface states filling in GaAs are also studied in these measurements.

关键词： terahertz carrier dynamics reflected wave