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CMOS-compatible high-index doped silica waveguide with an embedded silicon-nanocrystal strip for all-optical analog-to-digital conversion

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Photonics Research 2019年第10期7卷 1200-1208页

作者： YUHUA LI KUN ZHU ZHE KANG WAI LOK HO ROY DAVIDSON CHAO LU BRENT ELITTLE SAI TAK CHU Department of Physics City University of Hong KongHong KongChina Photonics Research Centre Department of Electronic and Information EngineeringThe Hong Kong Polytechnic UniversityHong KongChina qxp technology Inc. Xi’an 710119China State Key Laboratory of Transient Optics and Photonics XIOPMCASXi’an 710119China

Passive all-optical signal processors that overcome the electronic bottleneck can potentially be the enabling components for the next-generation high-speed and lower power consumption systems. Here, we propose and experimentally demonstrate a CMOS-compatible waveguide and its application to the all-optical analog-to-digital converter(ADC) under the nonlinear spectral splitting and filtering scheme. As the key component of the proposed ADC, a 50 cm long high-index doped silica glass spiral waveguide is composed of a thin silicon-nanocrystal(Si-nc) layer embedded in the core center for enhanced nonlinearity. The device simultaneously possesses low loss(0.16 dB/cm at 1550 nm), large nonlinearity(305 W^-1∕km at 1550 nm), and negligible nonlinear absorption.A 2-bit ADC basic unit is achieved when pumped by the proposed waveguide structure at the telecom band and without any additional amplification. Simulation results that are consistent with the experimental ones are also demonstrated, which further confirm the feasibility of the proposed scheme for larger quantization *** demonstrated approach enables a fully monolithic solution for all-optical ADC in the future, which can digitize broadband optical signals directly at low power consumption. This has great potential on the applications of high-speed optical communications, networks, and signal processing systems.

关键词： waveguide optical pumped

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Four-wave mixing in silicon-nanocrystal embedded high-index doped silica micro-ring resonator

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Journal of Semiconductors 2021年第4期42卷 104-110页

作者： Yuhua Li Xiang Wang Roy Davidson Brent E.Little Sai Tak Chu Key Laboratory of Optical Field Manipulation of Zhejiang Province Department of PhysicsZhejiang Sci-Tech UniversityHangzhou 310018China Department of Physics City University of Hong KongHong Kong 999077China qxp technology Inc. Xi’an 710119China State Key Laboratory of Transient Optics and Photonics XIOPMCASXi’an 710119China

A nonlinear integrated optical platform that allows the fabrication of waveguide circuits with different material composition,and at small dimensions,offers advantages in terms of field enhancement and increased interaction length,thereby facilitating the observation of nonlinear optics effects at a much lower power *** enhance the nonlinearity of the conventional waveguide structure,in this work,we propose and demonstrate a microstructured waveguide where silicon rich layer is embedded in the core of the conventional waveguide in order to increase its *** embedding a 20 nm thin film of silicon nanocrystal(Si-nc),we achieve a twofold increase of the nonlinear parameter,γ.The linear relationship between the fourwave mixing conversion efficiency and pump power reveals the negligible nonlinear absorption and small dispersion in the micro-ring *** simple approach of embedding an ultra-thin Si-nc layer into conventional high-index doped silica dramatically increases its nonlinear performance,and could potentially find applications in all-optical processing functions.

关键词： four-wave mixing silicon nanocrystal high-index doped silica micro-ring resonator

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Preface to the Special Issue on Semiconductor Optoelectronic Integrated Circuits

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Journal of Semiconductors 2021年第4期42卷 1-2页

作者： Wei Wang Lingjuan Zhao Dan Lu Jianping Yao Weiping Huang Yong Liu Brent Little Institute of Semiconductors Chinese Academy of SciencesBeijing 100083China School of Electrical Engineering and Computer Science University of OttawaOttawaOntarioCanada School of Information Science and Engineering Shandong UniversityJinan 250100China University of Electronic Science and technology Chengdu 610054China qxp Technologies Inc. Xi’an 710117China

The past 20 years have witnessed the rapid growth of photonic integration circuits(PIC)technology,which has been warmly embraced by both academia and the *** by the advanced development in material growth,processing,and design capability,the PIC technology now covers multiple material platforms,including III–V(InP,GaAs),silicon,silica,lithium niobate on insulator(LNOI)polymer,*** integration level has evolved from a single functional device to thousands of components *** increase in the performance and the complexity of the PICs have become an energetic booster for communication and information technology.

关键词： integration lithium silica

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Athermal third harmonic generation in micro‐ring resonators

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Opto-Electronic Advances 2020年第12期3卷 17-27页

作者： Shaohao Wang Yuhua Li Brent ELittle Leiran Wang Xiang Wang Roy RDavidson Sai Tak Chu FZU-Jinjiang Joint Institute of Microelectronics Jinjiang Science and Education ParkFuzhou UniversityJinjiang 362200China Department of Physics City University of Hong KongKowloon TongHong Kong 999077China State Key Laboratory of Transient Optics and Photonics Xi’an Institute of Optics and Precision MechanicsChinese Academy of SciencesXi’an 710119China University of Chinese Academy of Sciences Beijing 100049China qxp technology Xi’an 710311China Department of Microelectronics Science and technology Qi Shan CampusFuzhou UniversityFuzhou 350108China Key Laboratory of Optical Field Manipulation of Zhejiang Province Department of PhysicsZhejiang Sci-Tech UniversityHangzhou 310018China

Nonlinear high-harmonic generation in micro-resonators is a common technique used to extend the operating range of applications such as self-referencing systems and coherent communications in the visible ***,the generated high-harmonic emissions are subject to a resonance shift with a change in *** present a comprehensive study of the thermal behavior induced phase mismatch that shows this resonance shift can be compensated by a combination of the linear and nonlinear thermo-optics *** this model,we predict and experimentally demonstrate visible third harmonic modes having temperature dependent wavelength shifts between−2.84 pm/ºC and 2.35 pm/ºC when pumped at the *** providing a new way to achieve athermal operation,this also allows one to measure the thermal coefficients and Q-factor of the visible *** steady state analysis,we have also identified the existence of stable athermal third harmonic generation and experimentally demonstrated orthogonally pumped visible third harmonic modes with a temperature dependent wavelength shift of 0.05 pm/ºC over a temperature range of 12º*** findings promise a configurable and active temperature dependent wavelength shift compensation scheme for highly efficient and precise visible emission generation for potential 2f–3f self-referencing in metrology,biological and chemical sensing applications.

关键词： third-harmonic generation thermodynamics micro-resonators

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Structural Variation of an Atmospheric Heat Source over the Qinghai-Xizang Plateau and Its Influence on Precipitation in Northwest China

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Advances in Atmospheric Sciences 2009年第5期26卷 1027-1041页

作者：魏娜巩远发何金海 Shaanxi Provincial Climate Center Center for Plateau Atmospheric and Environmental Research Department of Atmospheric Science Chengdu University of Information Technology College of Atmosphere Sciences Nanjing University of Information Science and Technology

NCEP/NCAR reanalysis data and a 47-year precipitation dataset are utilized to analyze the relationship between an atmospheric heat source （hereafter called 〈 Q1 〉） over the Qinghai-Xizang Plateau （qxp） and its surrounding area and precipitation in northwest China. Our main conclusions are as follows：（1） The horizontal distribution of 〈 Q1 〉 and its changing trend are dramatic over qxp in the summer. There are three strong centers of 〈 Q1 〉 over the south side of qxp with obvious differences in the amount of yearly precipitation and the number of heat sinks predominate in the arid and semi-arid regions of northwest China （NWC）, beside the northern qxp with an obvious higher intensity in years with less precipitation. （2） In the summer, the variation of the heat source＇s vertical structure is obviously different between greater and lesser precipitation years in eastern northwest China （ENWC）. The narrow heat sink belt forms between the northeast qxp and the southwestern part of Lake Baikal. In July and August of greater precipitation years, the heating center of the eastern qxp stays nearly over 35°N, and at 400 hPa of the eastern qxp, the strong upward motion of the heating center constructs a closed secondary vertical circulation cell over the northeast qxp （40~ 46~N）, which is propitious to add precipitation over the ENWC. Otherwise, the heating center shifts to the south of 30°N and disappears in July and August of lesser precipitation years, an opposite secondary circulation cell forms over the northeast qxp, which is a disadvantage for precipitation. Meanwhile, the secondary circulation cell in years with more or less precipitation over the ENWC is also related to the heat source over the Lake Baikal. （3） The vertical structure of the heat source over the western qxp has obvious differences between greater and lesser precipitation years in western northwest China in June and July. The strong/weak heat source over the western qxp produces relatively strong/weak

关键词： Qinghai-Xizang Plateau atmospheric heat source/sink greater/lesser precipitation years,northwest China

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Modeling the East Asian climate during the last glacial maximum

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Science China Earth Sciences 2003年第10期46卷 1060-1068页

作者：赵平陈隆勋周秀骥巩远发韩余 Chinese Academy of Meteorological Sciences Beijing 100081 China Chengdu University of Information technology Chengdu 610041 China

Using the CCM3 global climate model of National Center for Atmospheric Research (NCAR), this paper comparatively analyzes the characteristics of East Asian monsoon and surface water condition and the expansion of glacier on the Qinghai-Xizang (Tibetan) Plateau (qxp) be-tween the present and the last glacial maximum (LGM). It is found that the winter monsoon is re-markably stronger during the LGM than at present in the north part of China and the western Pa-cific but varies little in the south part of China. The summer monsoon remarkably weakens in South China Sea and the south part of China during the LGM and has no remarkable changes in the north part of China between the present and the LGM. Due to the alternations of the monsoons during the LGM, the annual mean precipitation significantly decreases in the northeast of China and the most part of north China and the Loess Plateau and the eastern qxp, which makes the earth surface lose more water and becomes dry, especially in the eastern qxp and the western Loess Plateau. In some areas of the middle qxp the decrease of evaporation at the earth surface causes soil to become wetter during the LGM than at present, which favors the water level of local lakes to rise during the LGM. Additionally, compared to the present, the depth of snow cover in-creases remarkably on the most part of the qxp during the LGM winter. The analysis of equilib-rium line altitude (ELA) of glaciers on the qxp, calculated on the basis of the simulated tempera-ture and precipitation, shows that although a less decrease of air temperature was simulated dur-ing the LGM in this paper, the balance between precipitation and air temperature associated with the atmospheric physical processes in the model makes the ELA be 300—900 m lower during the LGM than at present, namely going down from the present ELA above 5400 m to 4600—5200 m during the LGM, indicating a unified ice sheet on the qxp during the LGM.

关键词： last glacial maximum, climatic simulation, East Asian monsoon, glacier on the Tibetan Plateau.

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Relationship between environmental evolution and human activities in the northeastern Qinghai-Xizang Plateau throughout the past millennium and its implications for the onset of the Anthropocene

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Science China Earth Sciences 2024年第11期67卷 3536-3549页

作者： Yang PU Xueqiong WEI Jianbao LIU Ke ZHANG Beibei LI Zhudeng WEI Mengmeng ZHANG Tong HE Yanjun WANG Xiaohua SHAO School of Geographical Sciences Nanjing University of Information Science and TechnologyNanjing 210044China Key Laboratory of Alpine Ecology Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China State Key Laboratory of Lake Science and Environment Nanjing Institute of Geography and LimnologyChinese Academy of SciencesNanjing 210008China

In current research on the Anthropocene, assessing the impact of human activities via stratigraphic records of sediments and demarcating the Anthropocene epoch globally are critical scientific issues that urgently need to be addressed. The northeastern Qinghai-Xizang Plateau(qxp), where humans first settled permanently in large numbers in the qxp, has varying sedimentary environments that are extremely sensitive to human activities. In contrast to other regions of the qxp, the northeastern sector boasts a richer array of climatic and environmental reconstruction sequences. This distinctive feature renders it an exemplary locale for investigating the stratigraphic boundary of the Anthropocene. Through in-depth analysis and integration of existing paleoclimate and paleoenvironment sequences in the northeastern qxp, we draw the following conclusions:(1) Throughout the past millennium, the impact of human activities on the environment of the northeastern qxp has become increasingly significant, especially in the past 200–300 years, gradually overshadowing climatic factors.(2) Since AD 1950,multiple physicochemical indicators related to human activities in the northeastern qxp have shown exponential growth,forming a distinct peak within the past millennium and clearly depicting the global “Great Acceleration” phenomenon and its development process.(3) Intensified human activities have driven swift environmental shifts and “decoupled” the interplay between climatic variations and the ecological environment, propelling the northeastern qxp into the “Early Anthropocene”from the “Late Holocene”. On the basis of the above findings, we construct a model suitable for identifying the stratigraphic boundary of the Anthropocene in the northeastern qxp and note that since the ecological environment in the northeastern qxp has entered the “Early Anthropocene”, the climate signals of certain physicochemical indicators in sediments are gradually becoming weaker, whereas the signals of

关键词： Anthropocene Qinghai-Xizang Plateau(qxp) Climate change Environmental evolution Human activities

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Vacuum and Air Flow for 2qxp-1 Vacuum Precision Seed Metering

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Journal of Northeast Agricultural University(English Edition) 2013年第2期20卷 61-64页

作者： Su Wei Wang Fu-lin Chen Hai-tao Lai Qing-hui Faculty of Modern Agricultural Engineering Kunming University of Science and Technology College of Engineering Northeast Agricultural University

Vacuum precision seed metering is the key part of vacuum seed planter. Planting performance of planter is affected by vacuum and air flow which are important parameters for choosing fan. Effects of qualification percent and miss percent on air chamber vacuum 3, 4, 5 and 6 kPa were studied at different operating speeds. The results showed that operating performance of the seed metering was excellent when air chamber vacuum was 5 and 6 kPa, which air flow was 7.4-8.0 m3·s-1 and 8.0-8.8 m3·s-1 , respectively.

关键词： seed planter precision seed metering vacuum degree air flow

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Recent advances in hydrology studies under changing permafrost on the Qinghai-Xizang Plateau

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Research in Cold and Arid Regions 2024年第4期16卷 159-169页

作者： Lu Zhou YuZhong Yang DanDan Zhang HeLin Yao State Key Laboratory of Frozen Soil Engineering Northwest Institute of Eco-Environment and ResourcesChinese Academy of SciencesLanzhouGansu 730000China Key Laboratory of Cryosphere Science and Frozen Soil Engineering Chinese Academy of SciencesLanzhouGansu 730000China University of Chinese Academy of Sciences Beijing 100049China College of Energy and Power Engineering Lanzhou University of TechnologyLanzhouGansu 730050China

Due to the great influences of both climate warming and human activities,permafrost on the Qinghai-Xizang Plateau(qxp) has been undergoing considerable *** degradation of plateau permafrost dramatically modifies the regional water cycle and hydrological processes,affecting the hydrogeological conditions,and ground hydrothermal status in cold *** thawing impacts the ecological environment,engineering facilities,and carbon storage functions,releasing some major greenhouse gases and exacerbating climate *** the utilization of advanced research methodologies to investigate the changing hydrological processes and the corresponding influencing factors in permafrost regions,there still exist knowledge gaps in multivariate data,quantitative analysis of permafrost degradation's impact on various water bodies,and systematic hydrological modeling on the *** review summarizes the main research methods in permafrost hydrology and elaborates on the impacts of permafrost degradation on regional precipitation distribution patterns,changes in surface runoff,expansion of thermokarst lakes/ponds,and groundwater dynamics on the ***,we discuss the current inadequacies and future research priorities,including multiple methods,observation data,and spatial and temporal scales,to provide a reference for a comprehensive analysis of the hydrological and environmental effects of permafrost degradation on the qxp under a warming climate.

关键词： Qinghai-Xizang Plateau Permafrost degradation Hydrological processes

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