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Defect Reduction in GaAs/Si Films with the a-Si Buffer Layer Grown by Metalorganic Chemical Vapor Deposition

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Chinese Physics Letters 2015年第8期32卷 165-168页

作者：王俊胡海洋贺云瑞邓灿王琦段晓峰黄永清任晓敏 institute of Information photonics and optical Communications Beijing University of Posts and Telecommunications State Key Laboratory of Information Photonics and Optical Communications Beijing 100876

The growth of GaAs epilayers on silicon substrates with a thin amorphous silicon （a-Si） buffer layer by met- alorganic chemical vapor deposition is investigated in detail. Combining with the two-step growth method, the growth conditions of the a-Si buffer layer are optimized for growth of high-quality GaAs//Si epilayers. The a-Si buffer layer exhibits the best effect with thickness of 1.8nm and growth temperature of 620℃. It is found that the introduction of this a-Si layer on Si substrates effectively reduces the dislocation density in GaAs//Si films. As compared with the dislocation density of 5 × 107 cm-2 in the GaAs/Si sample without the a-Si layer, a density of 3 × 105 cm-2 is achieved in the sample with the a-Si layer, and the defect reduction mechanism is discussed in detail.

关键词： Si

Fano-like resonance characteristics of asymmetric Fe_2O_3@Au core/shell nanorice dimer

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Chinese Physics B 2014年第8期23卷 474-480页

作者：王彬兵周骏张昊鹏陈金平 institute of photonics Faculty of Science Ningbo University

A geometrical configuration of Fe2O3/Au core-shell nanorice dimer is proposed and its multipolar plasmon Fano- like resonance characteristics are theoretically investigated by generalizing the plasmon hybridization model of individual nanorice to the bright and dark modes of the nanorice dimer. Under the irradiation of polarization light, the extinction spectra of the nanorice dimer are numerically simulated by using the finite element method （FEM）. Our studies show that the Fano-like resonance of the nanorice dimer results in an asymmetric line shape of the Fano dip in the extinction spectrum which can be controlled by varying the structure parameters of the nanorice dimer. Meanwhile, there is a giant field enhancement at the gap between the two nanorices on account of the plasmonic coupling in the nanorice dimer. The aforementioned two characteristics of the nanorice dimer are useful for plasmon-induced transparency and localized surface plasmon resonance sensors.

关键词： localized surface plasmon resonance field enhancement nanorice plasmon hybridization

Study on signal intensity of low field nuclear magnetic resonance via an indirect coupling measurement

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Chinese Physics B 2013年第4期22卷 36-39页

作者：蒋凤英王宁金贻荣邓辉田野郎佩琳李洁陈莺飞郑东宁 School of science Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications institute of Physics Chinese Academy of Sciences

We carry out an ultra-low-field nuclear magnetic resonance （NMR） experiment based on high-T c superconducting quantum interference devices （SQUIDs）. The measurement field is in a micro-tesla range （～10 μT-100 μT） and the experiment is conducted in a home-made magnetically-shielded-room （MSR）. The measurements are performed by the indirect coupling method in which the signal of nuclei precession is indirectly coupled to the SQUID through a tuned copper coil transformer. In such an arrangement, the interferences of applied measurement and polarization field to the SQUID sensor are avoided and the performance of the SQUID is not destroyed. In order to compare the detection sensitivity obtained by using the SQUID with that achieved using a conventional low-noise-amplifier, we perform the measurements using a commercial room temperature amplifier. The results show that in a wide frequency range （～1 kHz-10 kHz） the measurements with the SQUID sensor exhibit a higher signal-to-noise ratio. Further, we discuss the dependence of NMR peak magnitude on measurement frequency. We attribute the reduction of the peak magnitude at high frequency to the increased field inhomogeneity as the measurement field increases. This is verified by compensating the field gradient using three sets of gradient coils.

关键词： indirect coupling measurement superconducting quantum interference devices low field nuclearmagnetic resonance

Performance Investigation of All-optical NRZ-to-Manchester Format Conversion with SOA-MZI Based XOR Logic Gate

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Chinese Physics Letters 2011年第2期28卷 112-115页

作者： CHEN Jian-Bo ZHOU Rui ZHANG Qi YU Chong-Xiu XIN Xiang-Jun institute of Information photonics and optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876

All-optical format conversion between non-return-to-zero(NRZ)and the Manchester code is implemented by using an optical exclusive-OR(XOR)logic gate based on a semiconductor optical amplifier Mach-Zehnder Interferometer(SOA-MZI).There is 10 Gbit/s all-optical NRZ-to-Manchester conversion implemented in our simulation system and BER performance of the format conversion is *** performances of the converted Manchester coded signal are discussed in terms of transmission length and received optical power.

关键词： NRZ SOA Manchester

Dispersion flattened photonic crystal fiber with high nonlinearity for supercontinuum generation at 1.55 μm

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Chinese Optics Letters 2011年第4期9卷 9-13页

作者：郑龙张霞任晓敏马会芳施雷王亚苗黄永清 Key Laboratory of Information photonics and optical Communications Ministry of EducationInstitute of Optical Communications and OptoelectronicsBeijing University of Posts and Telecommunications

A robust design for a photonic crystal fiber （PCF） based on pure silica with small normal dispersion and high nonlinear coefficient for its dual concentric core structure is, presented. This design is suitable for flat broadband supercontinuum （SC） generation in the 1.55-μm region. The numerical results show that the nonlinear coefficient of the proposed eight-ring PCF is 33.8 W^-1·km^-1 at 1550 nm. Ultraflat dispersion with a value between -1.65 and -0.335 ps/（nm·km） is obtained ranging from 1375 to 1625 nm. The 3-dB bandwidth of the SC is 125 nm （1496-1621 nm）, with a fiber length of 80 m and a corresponding input peak power of 43.8 W. The amplitude noise is considered to be related to SC generation. For practical fabrication, the influence of the random imperfections of airhole diameters on dispersion and nonlinearity is discussed to verify the robustness of our design.

关键词： Crystal structure Crystal whiskers Design Dispersions Nonlinear optics optical fiber fabrication Photonic crystals Silica

Co-existence generation of XG-PON and single carrier XLG-PON for ultra-high definition TV transmission with entirely passive optical plant

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Optoelectronics Letters 2013年第3期9卷 221-224页

作者： Shahab Ahmad Niazi 张晓光席丽霞 Abid Munir Muhammad Idress State Key Laboratory of Information photonics and optical Communication Institute of Information Photonics and Optical Communication Beijing University of Posts and Telecommunications

International telecommunication union (ITU) recently has standardized ultra-high definition television (UHD-TV) with a resolution which is 16 times more than that of current high definition TV. Increasing the efficiency of video source coding or the capacity of transmission channels will be needed to deliver such programs by passive optical network (PON). In this paper, a complete passive co-existence of 10 Gbit-PON (XG-PON) and single carrier 40 Gbit-PON (XLG-PON) for overlay of UHD-TV distribution to 32 optical network units (ONUs) on broadcast basis is presented. The results show error free transmission performance with negligible power penalty over a 20 km bidirectional fiber.

关键词：高清电视传输信道单载波共存光学国际电信联盟无源光网络光网络单元

Practical continuous-variable quantum key distribution with feasible optimization parameters

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science China(Information sciences) 2023年第8期66卷 80-91页

作者： Li MA Jie YANG Tao ZHANG Yun SHAO Jinlu LIU Yujie LUO Heng WANG Wei HUANG Fan FAN Chuang ZHOU Liangliang ZHANG Shuai ZHANG Yichen ZHANG Yang LI Bingjie XU science and Technology on Communication Security Laboratory Institute of Southwestern Communication State Key Laboratory of Information photonics and optical Communications Beijing University of Posts and Telecommunications

Continuous-variable quantum key distribution(CV-QKD) offers an approach to achieve a potential high secret key rate(SKR) in metropolitan areas. There are several challenges in developing a practical CV-QKD system from the laboratory to the real world. One of the most significant points is that it is really hard to adapt different practical optical fiber conditions for CV-QKD systems with unified hardware. Thus,how to improve the performance of practical CV-QKD systems in the field without modification of the hardware is very important. Here, a systematic optimization method, combining the modulation variance and error correction matrix optimization, is proposed to improve the performance of a practical CV-QKD system with a restricted capacity of postprocessing. The effect of restricted postprocessing capacity on the SKR is modeled as a nonlinear programming problem with modulation variance as an optimization parameter,and the selection of an optimal error correction matrix is studied under the same scheme. The results show that the SKR of a CV-QKD system can be improved by 24% and 200% compared with previous frequently used optimization methods theoretically with a transmission distance of 50 km. Furthermore, the experimental results verify the feasibility and robustness of the proposed method, where the achieved optimal SKR achieved practically deviates <1.6% from the theoretical optimal value. Our results pave the way to deploy high-performance CV-QKD in the real world.

关键词： continuous-variable quantum key distribution post-processing optimization secret key rate

Growth of pure zinc blende p-type GaAs nanowires by metal-organic chemical vapor deposition

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Journal of Semiconductors 2011年第5期32卷 22-27页

作者：李然黄辉任晓敏郭经纬刘小龙黄永清蔡世伟 Key Laboratory of Information photonics and optical Communications Ministry of EducationBeijing University of Posts and Telecommunications Electronics science and Technology institute Dalian University of Technology

Vertical p-type gallium arsenide （GaAs） nanowires with pure zinc blende structure were grown on GaAs （111） B substrate by metal-organic chemical vapor deposition via a Au-catalyst vapor-liquid-solid mechanism. The p-type doping was investigated by additional diethyl zinc （DEZn）. In the high Ⅱ/Ⅲ ratio range （Ⅱ/Ⅲ〉9.1%）, there exists a critical length beyond which kinking takes place. Two possible reasons are discussed. Zn occurrence in the nanowires was verified by energy dispersive X-ray （EDX） analysis. Corresponding to Ⅱ/Ⅲ = 0.2%, the doping concentration is about 8 × 10^18 cm^-3.

关键词： GaAs nanowire p-type doping metal organic chemical vapor position zinc-blende structure

A hybrid-type quantum random number generator

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Chinese Physics B 2016年第5期25卷 49-52页

作者：马海强朱武韦克金李瑞雪刘宏伟 School of science and State Key Laboratory of Information photonics and optical Communications Beijing University of Posts and Telecommunications

This paper proposes a well-performing hybrid-type truly quantum random number generator based on the time interval between two independent single-photon detection signals, which is practical and intuitive, and generates the initial random number sources from a combination of multiple existing random number sources. A time-to-amplitude converter and multichannel analyzer are used for qualitative analysis to demonstrate that each and every step is random. Furthermore, a carefully designed data acquisition system is used to obtain a high-quality random sequence. Our scheme is simple and proves that the random number bit rate can be dramatically increased to satisfy practical requirements.

关键词： true random number generator single photon counting time interval