Target-adaptive optical phased array lidar

Lidar based on the optical phased array(OPA)and frequency-modulated continuous wave(FMCW)technology stands out in automotive applications due to its all-solid-state design,high reliability,and remarkable resistance to interference.However,while FMCW coherent detection enhances the interference resistance capabilities,it concurrently results in a significant increase in depth computation,becoming a primary constraint for improving point cloud density in such perception systems.To address this challenge,this study introduces a lidar solution leveraging the flexible scanning characteristics of OPA.The proposed system categorizes target types within the scene based on RGB images.Subsequently,it performs scans with varying angular resolutions depending on the importance of the targets.Experimental results demonstrate that,compared to traditional scanning methods,the target-adaptive method based on semantic segmentation reduces the number of points to about one-quarter while maintaining the resolution of the primary target area.Conversely,with a similar number of points,the proposed approach increases the point cloud density of the primary target area by about four times.

Silicon-based optical phased array with a reconfigurable aperture for“gaze”scanning of LiDAR

Light detection and ranging(LiDAR)serves as one of the key components in the fields of autonomous driving,surveying mapping,and environment detection.Conventionally,dense points clouds are pursued by LiDAR systems to provide high-definition 3D images.However,the LiDAR is typically used to produce abundant yet redundant data for scanning the homogeneous background of scenes,resulting in power waste and excessive processing time.Hence,it is highly desirable for a LiDAR system to“gaze”at the target of interest by dense scanning and rough sparse scans on the uninteresting areas.Here,we propose a LiDAR structure based on an optical phased array(OPA)with reconfigurable apertures to achieve such a gaze scanning function.By virtue of the cascaded optical switch integrated on the OPA chip,a 64-,128-,192-,or 256-channel antenna can be selected discretionarily to construct an aperture with variable size.The corresponding divergence angles for the far-field beam are 0.32°,0.15°,0.10°,and 0.08°,respectively.The reconfigurable-aperture OPA enables the LiDAR system to perform rough scans via the large beam spots prior to fine scans of the target by using the tiny beam spots.In this way,the OPA-based LiDAR can perform the“gaze”function and achieve full-range scanning efficiently.The scanning time and power consumption can be reduced by 1/4 while precise details of the target are maintained.Finally,we embed the OPA into a frequency-modulated continuous-wave(FMCW)system to demonstrate the“gaze”function in beam scanning.Experiment results show that the number of precise scanning points can be reduced by 2/3 yet can obtain the reasonable outline of the target.The reconfigurable-aperture OPA(RA-OPA)can be a promising candidate for the applications of rapid recognition,like car navigation and robot vision.

宏基因组学检测对肺部感染性疾病的诊断价值

目的分析12例体液标本宏基因组学检测对肺部感染性疾病的病原菌学诊断价值。方法回顾分析我科送检深圳华大基因检测公司检测的13份样本(肺泡灌洗液和外周血)基因检测结果,结合患者的临床资料以及临床治疗过程,评价宏基因组学检测对肺部感染性疾病的诊断价值。结果 12例患者中9例有基础病,标本中有5例外周血标本,8例肺泡灌洗液标本,有1例患者同步送检了血和肺泡灌洗液,有8例患者直接检出病原菌,结合病历资料进行临床分析,结果与临床相符,按结果调整治疗方案,患者治疗有获益。2例患者标本检出的病原菌与临床不相符。结论宏基因组测序方法能克服临床上微生物标本培养阳性率低的困难,为肺部感染性疾病提供有效的抗生素指导。

Legislation on protection of drinking water sources and local management practices in the Pearl River Delta region of China

The protection of drinking water sources is vital to urban development and public health.In this study,the current situation of the mandatory protection area for drinking water source in the Pearl River Delta region was investigated using a method combining Google Earth with the field survey.The gaps between management practices and legislation requirements were analyzed.Finally,several countermeasures for water resource protection were proposed as follows:to promote delineation in a more scientific way,to safeguard the sanctity of the law,to make better plan on water saving,and to encourage public participation in supervision and management.

Three-terminal germanium-on-silicon avalanche photodiode with extended p-charge layer for dark current reduction

Germanium-on-silicon(Ge-on-Si) avalanche photodiodes(APDs) are widely used in near-infrared detection, laser ranging, free space communication, quantum communication, and other fields. However, the existence of lattice defects at the Ge/Si interface causes a high dark current in the Ge-on-Si APD, degrading the device sensitivity and also increasing energy consumption in integrated circuits. In this work, we propose a novel surface illuminated Ge-on-Si APD architecture with three terminals. Besides two electrodes on Si substrates, a third electrode is designed for Ge to regulate the control current and bandwidth, achieving multiple outputs of a single device and reducing the dark current of the device. When the voltage on Ge is -27.5 V, the proposed device achieves a dark current of 100 n A, responsivity of 9.97 A/W at -40 d Bm input laser power at 1550 nm, and optimal bandwidth of 142 MHz. The low dark current and improved responsivity can meet the requirements of autonomous driving and other applications demanding weak light detection.

On-chip generation of Bessel–Gaussian beam via concentrically distributed grating arrays for long-range sensing

Bessel beam featured with self-healing is essential to the optical sensing applications in the obstacle scattering environment.Integrated on-chip generation of the Bessel beam outperforms the conventional structure by small size,robustness,and alignment-free scheme.However,the maximum propagation distance(Z_(max))provided by the existing approaches cannot support long-range sensing,and thus,it restricts its potential applications.In this work,we propose an integrated silicon photonic chip with unique structures featured with concentrically distributed grating arrays to generate the Bessel-Gaussian beam with a long propagation distance.The spot with the Bessel function profile is measured at 10.24m without optical lenses,and the photonic chip’s operation wavelength can be continuously performed from 1500 to 1630 nm.To demonstrate the functionality of the generated Bessel-Gaussian beam,we also experimentally measure the rotation speeds of a spinning object via the rotational Doppler Effect and the distance through the phase laser ranging principle.The maximum error of the rotation speed in this experiment is measured to be 0.05%,indicating the minimum error in the current reports.By the compact size,low cost,and mass production potential of the integrated process,our approach is promising to readily enable the Bessel-Gaussian beam in widespread optical communication and micro-manipulation applications.

Wide-steering-angle high-resolution optical phased array

Optical phased array(OPA)technology is considered a promising solution for solid-state beam steering to supersede the traditional mechanical beam steering.As a key component of the LIDAR system for long-range detection,OPAs featuring a wide steering angle and high resolution without beam aliasing are highly desired.However,a wide steering range requires a waveguide pitch less than half of the wavelength,which is easily subjected to cross talk.Besides,high resolution requires a large aperture,and it is normally achieved by a high count number of waveguides,which complicates the control system.To solve the mentioned issues,we design two high-performance 128-channel OPAs fabricated on a multilayered SiN-on-SOI platform.Attributed to the nonuniform antenna pitch,only 128 waveguides are used to achieve a 4 mm wide aperture.Besides,by virtue of innovative dual-level silicon nitride(Si_(3)N_(4))waveguide grating antennas,the fishbone antenna OPA achieves a 100°×19.4°field of view(FOV)with divergence of 0.021°×0.029°,and the chain antenna OPA realizes a 140°×19.23°FOV with divergence of 0.021°×0.1°.To our best knowledge,140°is the widest lateral steering range in two-dimensional OPA,and 0.029°is the smallest longitudinal divergence.Finally,we embed the OPA into a frequency-modulated continuous-wave system to achieve 100 m distance measurement.The reflected signal from 100 m distance is well detected with 26 dBm input transmitter power,which proves that OPA serves as a promising candidate for transceiving optical signal in a LIDAR system.

Iron polyphthalocyanine-derived ternary-balanced Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 as a high-performance electrocatalyst for the oxygen reduction reaction

The oxygen reduction reaction (ORR) is the cornerstone reaction of the cathode in metal±air batteries;however,slow kinetics requires high-performance catalysts to promote the reaction.Polyphthalocyanine (PPc) has a typical chemical cross-linking structure and uniformly dispersed metal active sites,but its poor activity and conductivity limit its applications as an ORR catalyst.Herein,a manageable and convenient strategy is proposed to synthesize ternary ORR catalysts through the low-temperature pyrolysis of Fe PPc.The optimal catalyst,Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5,exhibits excellent ORR activity in alkaline solution with a half-wave potential of 0.90 V,which is significantly higher than that of commercial 20%Pt/C (0.84 V).Electrochemical tests and extended X-ray absorption fine structure spectroscopy reveal that the superior ORR activity of Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 could be ascribed to the balance of its ternary components(i.e.,Fe_(3)O_(4),Fe_(3)N,and Fe-N;species).A Zn±air battery incorporating Fe_(3)O_(4)/Fe_(3)N/Fe-N-C@PC-2.5 as an air cathodic catalyst delivers a high open-circuit voltage and peak power density.During galvanostatic discharge,the battery demonstrates a specific capacity of 815.7 mA h g^(-1).The facile strategy of using PPc to develop high-performance composite electrocatalysts may be expanded to develop new types of catalysts in the energy field.

Assessing high resolution oxidation-reduction potential and soluble reactive phosphorus variation across vertical sediments and water layers in Xinghu Lake:A novel laboratory approach

To understand the transfer process of soluble reactive phosphorus （SRP） on the lake sediment-water interface in a mesotrophic shallow lake in South China, the SRP concentrations and the oxidation-reduction potential （ORP） across the sediment-water interfaces were continually monitored. Sediment samples were collected from Xinghu Lake in Guangdong Province. The ORP dynamics at different layers of overlying water was similar for six experimental systems, whereas those in porewater were significantly different. The ORP in overlying water was 200-300 mV higher than those in sediments. The oxygen penetration depth ranged from 2 to 10 mm in Xiannu Lake sediments. The variation amplitudes of ORP increased with sediment depth, but the mean ORP values were all about 218 mV. The SRP concentrations in porewater maintained at a low level of about 0.049 mg/L because of high atom ratio of total iron and total manganese to total phosphorus. The SRP concentrations and variation amplitudes in porewater increased with sediment depth. The SRP in overlying water mainly originated from S RP transference of the porewater of middle and bottom sediments （3-15 cm）. The ORP variation and SRP transfer in porewater played important roles in changing SRP concentrations. A distinct SRP concentration gradient appeared in overlying water when intense exchange occurred at the sediment-water interface; therefore, it was necessary to monitor the SRP concentration profiles to accurately estimate the internal loading.

Oxidation State as a Descriptor in Oxygen Reduction Electrocatalysis

Electrocatalysts for the oxygen reduction reaction(ORR)are critically important in the development of fuel cells and metal-air batteries.Intensive research interests have been devoted to improving the electrocatalytic performance by tuning the morphology and defect-active sites.Herein,we demonstrate that the oxidation state can also serve as an effective strategy for designingORR electrocatalysts.Valencemodels of silver with gradient chemical valence from zero valence to trivalence were successfully built.Their oxidation states were evaluated by cryo-X-ray photoelectron spectroscopy,X-ray absorptionfinestructure,and electron paramagnetic resonance spectroscopy.For the first time,our results demonstrated that the electrocatalytic activities of silver species can be improved by increasing their valence,conforming the orderofAg<Ag_(2)O<Ag_(2)O_(2)<Ag_(3)O_(4)<Ag_(2)O_(3).Computational studies reveal that higher valence Ag species possess a higher proportion of d band holes andmore electrons closer to the Fermi level.Therefore,the oxygen adsorption and activation energy on the Ag sites can be regulated to a near-optimal level and the ORR catalytic efficiency increases.This work clearly presents that oxidation state is another degree of freedom in designing efficient ORR electrocatalysts.