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In recent decades, dual-band photodetectors have received widespread attention due to better target identification, which are considered as the development trend of next generation photodetectors. However, the traditional dual-band photodetectors based on heteroepitaxial growth, superlattice and multiple quantum well structures are limited by complex fabrication process and low integration. Herein, we report a UV/IR dual-band photodetector by integrating ultra-wide gap β-Ga2O3 and narrow-gap black phosphorous(BP) nanoflakes. A vertical van der Waals (vdW) heterostructure is formed between BP and β-Ga2O3 by mechanically exfoliated method integrated without the requirement of lattice match. The heterostructure devices show excellent rectification characteristics with high rectifying ratio of ca. 106 and low reverse current around pA. Moreover, the device displays obvious photoresponse under UV and IR irradiations with responsivities of 0.87 and 2.15 mA/W, respectively. We also explore the band alignment transit within the heterostructure photodetector at different bias voltages. This work paves the way for fabricating novel dual-band photodetectors by utilizing 2D materials.

With the technological development of stereoscopic display, an immersive 3D space with large size can be reconstructed more and more easily, and a 3D spatial interaction method with high-efficiency become more and more urgent. Gesture interaction, as the most natural and efficient way of human-computer interaction, can convey information very quickly and efficiently. However, the effective interaction distance of most existing gesture interaction methods is less than one meter, and can not meet the demand of the long distance 3D spatial interaction. In this paper, an efficient network named Gesture YOLO for long-distance gesture detection is proposed to achieve the small gesture object detection with improved accuracy. There are two modules in our Gesture YOLO, one is the Dual CSPDarknet53-tiny Backbone module for fusing person features and gesture features, and the other is the Progressive Multi-Scale Feature Fusion module for enhancing output features. The experimental results on our test set show that our Gesture YOLO can achieve higher gesture detection accuracy than the YOLOv4-tiny at distances ranging from 2m to 5m, and can mitigate the significant drop in gesture detection accuracy when the distance increases.

We demonstrate a structure design of electrically pumped 1.3 μm InAs/InGaAs quantum dot microdisk lasers on silicon with an output waveguide . Three-dimensional finite-difference time-domain method is used to numerically analyze the mode characteristics of the microdisk lasers. The effects of the diameter of microdisk cavity, the thickness of cladding layer, the etching depth and the waveguide width on the quality factor (Q-factor) are studied in detail. The results show that when the microdisk laser with a diameter of 7 μm, a thickness of cladding layer of 1.75 μm, an etching depth of 4.53 μm and a waveguide width of 0.5 μm, the Q-factor is maximized. The mode wavelength and the mode quality factor are 1304.45 nm and 19133, respectively. The photoelectric properties of InAs/InGaAs quantum dot microdisk lasers are simulated by rate equations.

Wastewater treatment plants (WWTP) are the important source of microplastics (MPs) in the environment, but the distribution and property of MPs in WWTPs are not fully understood. The study systematically investigated the transportation, characteristics and fate of MPs in both sewage and sludge of WWTP in Xi'an, a western region of China to complement the research on the fate of MPs in WWTP in inland China. The consequence was abundance, size, shape, color and type of MPs in sewage and sludge of different treatment processes were analyzed and compared by the metallurgical microscope and Fourier Transform Infrared (FTIR) spectrometer. Results showed that the MP abundance decreased from 288.5 n/L of the influent to 22.9 n/L of the effluent, corresponding to the removal rate of 92.1%. Among them, the secondary treatment has the best removal effect, with a removal rate of 72.1%. With the treatment process, the distribution of MPs with different characteristics is constantly changing, which leads to differences in the distribution of MPs in sludge and sewage. It is speculated from the characteristics of MPs that domestic sewage is still the main source of microplastics in Beishiqiao WWTP. Restricting the use of plastic products in daily life or finding alternatives is of great significance to the construction of MPs pollution.

Recent researches on object segmentation mostly concentrate on single-view images or objects in 3D settings. In this paper, a novel method for efficient multi-view foreground object segmentation is presented, using spatial consistency across adjacent views as constraints to generate identical masks. Even though the conventional segmentation results at different views are relatively accurate, there always are inconsistent regions where the boundaries of the mask are different over the same area across multiple views. The central idea of our method is to utilize the camera parameters to guide the refocusing procedure, during which each instance across different views is refocused using multi-view projections. The refocused images are then used as the input of instance segmentation network to predict the bounding box and object mask. The final step takes the network output as the prior information for the GMMs to achieve more accurate segmentation results. While many concrete implementations of the general idea are feasible, satisfactory results can be achieved with this simple and efficient approach. Experimental results demonstrate both qualitatively and quantitatively that the proposed method outputs excellent results with less background pixels, thus allowing us to improve the 3D display quality eventually. We hope this simple and effective method can be of help to future researches in relevant tasks.

In the optical networks, the dynamicity, the complexity and the heterogeneity have dramatically increased owing to the deployment of advanced coherent techniques, and the optical cross-connect technologies and diverse network infrastructures pose great challenges in the optical network management and maintenance for the network operators. In this review, we propose a “3S” architecture for AI-driven autonomous optical network, which can aid the optical networks operated in “self-aware” of network status, “self-adaptive” of network control, and “self-managed” of network operations. To support these functions, a number of artificial intelligence (AI)-driven techniques have been investigated to improve the flexibility and the reliability from the device aspect to network aspect. Adaptative erbium-doped fiber amplifier (EDFA) controlling is an example for the device aspect, which provides a power self-adaptive capability according to the network condition. From the link aspect, adaptive fiber nonlinearity compensation, optical monitoring performance and quality of transmission estimation are developed to monitor and alleviate the link-dependent signal impairments in an automatic way. From the network aspect, traffic prediction and network state analysis methods provide the self-awareness, while automatic resource allocation and network fault management powered by AI enhance the self-adaptiveness and self-management capabilities. Benefit from the sufficient network management data, powerful data-mining capability and matured computation units, these AI techniques have great potentials to provide autonomous features for optical networks, including the network resource scheduling and the network customization.

We propose and numerically analyze a broadband and high extinction ratio mode converter to achieve the mode conversion between the fundamental transverse electric mode (TE0) and the first-order transverse magnetic mode (TM1). The mode converter is achieved by using the tapered hybrid plasmonic waveguide which the metal is directly covered on the Si waveguide without a thin low-index layer. After optimizing the structure of the tapered hybrid plasmonic waveguide, a wide operation bandwidth of 100 nm is obtained with the extinction ratio of the TM1 mode and TE0 mode larger than 20 dB in the output Si waveguide for the forward propagation. And for the back propagation, the operation bandwidth over 65 nm is obtained with the extinction ratio larger than 20 dB in the output Si waveguide. The whole footprint of the mode converter is only 0.8 × 11 μm2. Fabrication tolerance analysis is also demonstrated.

We report a structure design of 1.55 μm square microcavity lasers monolithically integrated on GaAs substrates. The mode characteristics of the microcavity lasers are numerically investigated by three-dimensional finite-difference time-domain method. The dependences of the high-quality factor modes on the side length of the microcavity, the width of the output waveguide and the etching depth are investigated in detail. The results demonstrate, for the microcavity structure with the side length of 12 μm, the output waveguide width of 1.0 μm and the etching depth of 3.55 μm, it is optimal to excite high-quality factor modes around wavelength of 1.55 μm. The mode wavelength and the mode quality factor are 1547.46 nm and 2416.28, respectively. The quality factor degrades rapidly with the waveguide width increasing, and increases with increasing etching depth.

Epitaxial lateral overgrowth (ELO) of 1.8-μm InP films was performed on nanopatterned GaAs (001) substrates via metal–organic chemical vapor deposition. Parallel SiO2 trenches with a nano-scale width (∼ 170 nm) and various seed line orientations of [110], [410], [010] and [4–10] were first adopted to optimize the growth in our work. Scanning electron microscopy, atomic force microscopy and double-crystal x-ray diffraction were used to characterize the as-grown InP/GaAs heterostructures. The results reveal that the surface morphology and crystalline quality are strongly affected by the seed line orientations, and both of these parameters are optimized under the orientation of the [4–10] direction. A low average full width at half maximum of 285.1 arcsec and a root mean square surface roughness of 2.95 nm are obtained for the 1.8-μm InP film. To clearly observe the initial coalescence stage during the growth processes, thinner (500 nm) ELO InP films were also grown. We found that the seed line orientation has a significant effect on the lateral growth rate and affects the quality of the final InP/GaAs epilayer.

We, first, demonstrate an optimized structure design and analyze the optical mode properties of 1.3 μm wavelength square microcavity lasers on silicon with InAs/InGaAs quantum-dot active region and mid-point output waveguides. Si-based square microcavities with whispering-gallery-like modes have been proposed for optimizing their quality factors (Q factors). Three-dimensional finite-difference time-domain method is used to numerically analyze the optical mode characteristics. The influences of the side-length of the microcavity, the output waveguide width, and the etching depth on the optical modes of the microcavity are investigated in detail. It indicates that the Q factor increases with increasing etching depth, and decreases rapidly as the waveguide width increases. The results show that with the side length of 18 μm, the waveguide width of 1.0 μm, and the etching depth of 3.5 μm, the Q factor is the highest, and the mode distribution is optimal. The mode wavelength and Q factor are 1305.9 nm and 4694.8, respectively. Advantages of more stable and evenly distributed mode profiles for Si-based square microcavity lasers have been demonstrated, and compared with the Si-based disk microcavity (microdisk) lasers. It promises a potential alternative laser structure for Si-based optoelectronic integration.

Hand, foot, and mouth disease (HFMD) is well recognized as one of the major threats to children's health globally. The increasing complexity of the etiology of HFMD still challenges disease control in China. There is little surveillance of the molecular epidemiological characteristics of the enteroviruses (EVs) that cause HFMD in Neijiang city or the Sichuan Basin area in Southwest China. In this study, demographic and epidemiological information for 14,928 probable HFMD cases was extracted and analyzed to describe the epidemic features of HFMD in Neijiang city from Jan 2010 to Dec 2017. The swab samples of select probable HFMD cases from 2012 to 2017 were tested by reverse transcription (RT) real-time PCR to identify the serotype distribution of EVs, and 110 randomly selected RT-real-time PCR positive samples were then amplified and analyzed for the VP1 or VP4 regions of EVs to further analyze the phylogenetic characteristics of the circulating strains in this area. The eight-year average annual incidence was 49.82 per 100,000 in Neijiang. The incidence rates varied between 19.51 and 70.73 per 100,000, demonstrating peaks of incidence in even-number years (2012, 2014 and 2016). The median age of the probable cases was 27 months and the interquartile range (25th to 75th percentile) of ages for the probable HFMD cases was between 14 and 42 months. The male-to-female ratio of the probable HFMD cases was 1.47:1, and scattered children were the major population classification (81.7%). Two epidemic peaks were observed: one major peak between April and July and the other lesser peak between October and December. Of 6513 probable cases tested with RT-real-time PCR, 4015 (61.6%) were positive for enterovirus with the serotype distribution as follows: EV71+, 30.1% (n = 1210); CV-A16+, 28.7% (n = 1154) and a sole pan-enterovirus+, 41.1% (n = 1651). A total of 91 cases (82.7%, 91/110) were successfully amplified and underwent phylogenetic analysis: all EV71+ cases were C4a serotype (n = 23/30); all CV-A16+ cases were B2b serotype (n = 24/30); of 42 sole pan-enterovirus+ samples, 20 were CV-A6, 14 were CV-A10 and the rest within this group were CV-A4 (n = 4), CV-A8 (n = 2), CV-A9 (n = 1) and CV-B3 (n = 1). Our findings provide important evidence that aids the improvement of strategies for vaccination against HFMD and comprehensive disease control in China.

The huge and ever-increasing data traffic promotes the upgradation of IP bearer network to possess higher transmission capability. As a long-term task, network upgradation needs to be implemented in multiple stages. At each stage, one or more network partitions are planned to meet various requirements in different areas or periods to realize the smooth change from the current network to the targeted one. However, how to select proper network partitions is an open question. Existing approaches are usually infeasibly applied to large-scale networks or neglect the characteristics of IP bearer network. In this paper, we present a hierarchical community discovery method to find network partitions for nodes to be upgraded. We transform the issue of hierarchy identification on the whole network into node role classification, which is addressed by training a classifier utilizing network centrality, label, and attribute information. Then, a novel community detection algorithm through semi-local expansion is proposed, with the geographical location also taken into consideration. Experiments are conducted on three real-world datasets. The results show the effectiveness of our method in node role classification task that at least 90% Micro-F1 score can be got with only 30% labeled nodes on the given networks. The attained community is adjustable with the size proportional to the parameter α and has a high modularity score. Moreover, our communities strictly comply with the affiliation in IP bearer network and preserve the integrity of the tree/ring structures.

Black phosphorous (BP), an excellent two-dimensional (2D) monoelemental layered p-type semiconductor material with high carrier mobility and thickness-dependent tunable direct bandgap structure, has been widely applied in various devices. As the essential building blocks for modern electronic and optoelectronic devices, high quality PN junctions based on semiconductors have attracted widespread attention. Herein, we report a junction field-effect transistor (JFET) by integrating narrow-gap p-type BP and ultra-wide gap n-type β-Ga2O3 nanoflakes for the first time. BP and β-Ga2O3 form a vertical van der Waals (vdW) heterostructure by mechanically exfoliated method. The BP/β-Ga2O3 vdW heterostructure exhibits remarkable PN diode rectifying characteristics with a high rectifying ratio about 107 and a low reverse current around pA. More interestingly, by using the BP as the gate and β-Ga2O3 as the channel, the BP/β-Ga2O3 JFET devices demonstrate excellent n-channel JFET characteristics with the on/off ratio as high as 107, gate leakage current around as low as pA, maximum transconductance (g m) up to 25.3 µS and saturation drain current (I DSS) of 16.5 µA/µm. Moreover, it has a pinch-off voltage of –20 V and a minimum subthreshold swing of 260 mV/dec. These excellent n-channel JFET characteristics will expand the application of BP in future nanoelectronic devices.

With the rapid development of Internet and communication systems, both in the aspect of services and technologies, communication networks have been suffering increasing complexity. It is imperative to improve intelligence in communication networks, and several aspects have been incorporating with Artificial Intelligence (AI) and Machine Learning (ML). The optical network, which plays an important role both in core and access network in communication networks, also faces great challenges of system complexity and the requirement of manual operations. To overcome the current limitations and address the issues of future optical networks, it is essential to deploy more intelligence capability to enable autonomous and flexible network operations. ML techniques are proved to have superiority on solving complex problems, and thus recently, ML techniques have been used for many optical network applications. In this paper, a detailed survey of existing applications of ML for intelligent optical networks is presented. The applications of ML are classified in terms of their use cases, which are categorised into optical network control and resource management, and optical network monitoring and survivability. These applications are analyzed and compared according to the used ML techniques. Besides, a tutorial for ML applications is provided from the aspects of the introduction of common ML algorithms, paradigms of ML, and motivations of applying ML. Lastly, challenges and possible solutions of ML application in intelligent optical networks are also discussed, which intends to inspire future innovations in leveraging ML to build intelligent optical networks.

A polarization beam splitter is proposed using silicon-nitride-assisted three-waveguide couplers. With 7 μm coupling length, the extinction ratios are more than 30 dB and insertion losses are less than 0.15 dB at 1.55 μm wavelength.

In this work, a technique for the growth of GaAs epilayers on Si, combining an ultrathin amorphous Si buffer layer and a three-step growth method, has been developed to achieve high crystalline quality for monolithic integration. The influences of the combined technique for the crystalline quality of GaAs on Si are researched in this article. The crystalline quality of GaAs epilayer on Si with the combined technique is investigated by scanning electron microscopy, double crystal X-ray diffraction (DCXRD), photoluminescence, and transmission electron microscopy measurements. By means of this technique, a 1.8-µm-thick high-quality GaAs/Si epilayer was grown by metal–organic chemical vapor deposition. The full-width at half-maximum of the DCXRD rocking curve in the (400) reflection obtained from the GaAs/Si epilayers is about 163 arcsec. Compared with only using three-step growth method, the current technique reduces etch pit density from 3 × 106 cm−2 to 1.5 × 105 cm−2. The results demonstrate that the combined technique is an effective approach for reducing dislocation density in GaAs epilayers on Si.

The GaAsP/Si dual-junction solar cells have been systematically investigated in our paper by using AMPS (Analysis of Microelectronic and Photonic Structures). Based on the optimized results of single-junction solar cells, we propose a promising method to improve the properties of the dual-junction solar cell. And the monolithic GaAs x P 1−x /Si dual-junction solar cells with various As compositions (x=0.65, 0.75, 0.85) and base thicknesses (t b =0.05∼2.5um) were analyzed. The remarkable conversion efficiency of 35.8% has been obtained for the GaAs 0.75 P 0.25 /Si dual-junction solar cells, which is higher than previously reported results. Our method and results will provide a significant guidance for the design and manufacture of Si-based dual-junction solar cells.

We report a 1.55μΜ square microcavity laser monolithically integrated on GaAs substrates. The mode characteristics of the microcavity laser are numerically investigated by three-dimensional finite difference time domain method. The dependences of the whispering-gallery modes on the width of the output waveguide and the etching depth are discussed. For the cavity with the side length of 12μm and the output waveguide of 1μm, it is easy to excite whispering-gallery modes around 1.55μm. The mode wavelength is 1542.88nm and the mode Q factor is 2389.23. The Q factor degrades rapidly with the waveguide width increasing and increases with the increasing of the etching depth.

We design two types of output waveguide structures based on bus waveguide: waveguide overlapping with microdisk cavity and single-ended output bus waveguide. This is the first time that these two output structures have been designed for microdisk lasers on silicon. Three-dimensional finite-difference time-domain method is used to numerically analyze the optical mode characteristics of the microdisk lasers. The quality factor (Q-factor) and optical mode distribution of microdisk lasers are calculated in detail. The photoelectric properties of microdisk lasers with different output structures are simulated by rate equations, which provide evidence for lasing. For the first time, by comparing the differences between the two output structures, we identify the respective characteristics of these two structures: microdisk lasers with the waveguide overlaps with the microdisk cavity are suitable for vertical coupling devices when the notch width is 3.5 μm and the waveguide width is 1.5 μm. And the single-ended bus waveguide output structure changes the bus waveguide structure from two-ended to single-ended, which meets the requirement of laser directional output.

We have designed three mode order converters using the sub-wavelength grating on the silicon-on-insulator substrate. The proposed mode order converters can separately realize the mode order conversion from the fundamental transverse electric mode to the first-order transverse electric mode (TE0-to-TE1), the second-order transverse electric mode (TE0-to-TE2) and the third-order transverse electric mode (TE0-to-TE3) with compact device sizes and good performances. The simulation results show that the mode order conversion efficiencies of TE0-to-TE1, TE0-to-TE2 and TE0-to-TE3 are larger than 94.4%, 95.7% and 83.7% in the wavelength ranging from 1.5 µm to 1.6 µm, the corresponding device length are 8.72 µm, 4.98 µm and 14.54 µm. In addition, the mode order converter can be fabricated with only once etching which will be advantage to the device fabrication.

A black arsenic-phosphorus saturable absorber (SA) was fabricated and experimentally applied for a passively Q-switched Er-doped fiber laser for the first time to the best of our knowledge. The high-quality black arsenic-phosphorus crystals were synthesized by the mineralizer-assisted chemical vapor transport (CVT) method, and the fewer-layer black arsenic-phosphorus thin film nanosheet SA was performed by a unique electrochemical delamination exfoliation procedure. Meanwhile, a stable passively Q-switched pulse was proposed based on the SA modified Er-doped ring fiber cavity, which had the repetition rate of 38.47 kHz, corresponding to a minimum pulse width of 5.26 µs, and a corresponding output power as high as 3.68 mW was obtained. The results suggest that black arsenic-phosphorus is a good choice to make practical two-dimensional saturable absorbers for potential ultrafast photonic applications due to its designable bandgap value and excellent optical characteristics.

We demonstrate firstly an optimized InAs/InGaAs quantum-dot microdisk laser structure on silicon. The simulations indicate that Q-factor can exceed 106 at wavelength of with the diameter and the cladding layer thickness of 7μm and 1.75μm.

In this article, anti-reflection coatings (ARCs) with double-layer metal nanoparticles for Cu(In, Ga)Se2 (CIGS) solar cells were proposed. A study of three ARCs nanostructures (Ag-SiO2-Ag, Au-SiO2-Au and Au-SiO2-Ag structures) on CIGS solar cells was presented using the finite-difference time-domain method. Various ARC nanostructures with different metals (Au and Ag), metal nanoparticle radius, spacing layer (SiO2) thickness, and period (corresponding to the particle density) on CIGS solar cells were optimized in detail. The Au-SiO2-Ag structure was demonstrated to have a better anti-reflection ability when the thickness of the SiO2 layer is 45 nm, the radius of the metal particle is 14 nm, and the side length of the period is 41 nm. The results demonstrated that the reflectivity of the CIGS solar cells with the optimal ARCs structure was reduce by 83% compared with the case of no ARCs. And compared with the MgF2 anti-reflection film, the reflectivity was reduced by 37%.

A 1.55 µm nanoscale laser array is proposed and designed on v-groove patterned Si (0 0 1) substrates. The laser array is designed by taking full advantage of the periodic groove structures of the patterned substrates. The periodic groove structures separated by a SiO2 mask can effectively reduce threading dislocation density in the active region and provide a strong lateral optical confinement for the laser array structure. The optical mode distributions of the single laser are investigated in detail, and the optical confinement factor is calculated to optimize the structure parameters of the laser array. An optimal value of 9.3% for the optical confinement factor is obtained. The analysis of threshold conditions shows that the laser array can achieve lasing with a cavity length of about 1 mm for an internal loss of 40 cm−1.

Junggar basin, located in the northwest arid areas of China, has vulnerable supergene ecological environment because of natural and anthropic factors. In this paper, based on the relationship between groundwater and ecological environment and combined with natural and geographical conditions, Junggar basin is divided into five ecosystem types: mountain, natural oasis, artificial oasis, natural water and desert. According to the above five ecosystem types, ecosystem zone maps of Junggar basin in 1990, 2000 and 2009 are obtained by interpreting remote sensing images from Landsat based on RS(Remote Sensing)and GIS(Geographic Information System). On the basis of ecosystem zone maps of three periods, evolution law of ecological environment in Junggar basin is concluded and some existing problems of ecological environment, caused by ecological environment change of three periods, are analyzed.

Due to exposed to serious pollution and influence of natural conditions, drinking water safety has become a hotspot issue drawing high attention from the state and government. Yinchuang Plain is in serious quality-induced water shortage. Through investigation and analysis, this paper established a drinking water safety evaluation system from the perspective of headwaters and human health, studying quality and quantity of groundwater, as well as geological protective performance; safety evaluation on groundwater exploration for drinking in Yinchuan Plain was conducted by adopting analytic hierarchy process and overlay and index methods with the help of GIS software platform. The evaluation result has practical significance for groundwater resource protection and groundwater safety supply.