Laser & Optoelectronics Progress
Co-Editors-in-Chief
Dianyuan Fan
Aoyang Wang, Xiangsheng Yu, and Guang Yuan

The development of self-frequency doubling lasers has been significantly limited owing to the thermal effect. To reduce the thermal effect of lasers and obtain higher beam quality yellow laser output, a Yb∶YCOB self-frequency doubling crystal yellow laser pumped by a 1020-nm laser is proposed. The influence of the thermal lens effect, because of the self-frequency doubling crystal-absorbing pump light energy, on the phase matching condition during the process of optical frequency doubling is explained on the basis of a theoretical analysis. Furthermore, the analysis also yields an explanation for the improvement in the quality of the 1020-nm single-band pumping mode beam, as compared with that of the traditional 976-nm laser diode pumping mode. A 570-nm yellow laser with higher beam quality is obtained through experiments. The beam quality factors correspond to Mx2=1.41 and My2=1.87. The results indicate that the quality of the outgoing beam at a wavelength of 1020 nm is significantly higher than that at 976 nm, and the spectrum width is narrower. The results of the study play a guiding role in reducing the thermal effect of Yb∶YCOB self-frequency doubling lasers and obtaining high-power yellow lasers with higher beam quality and narrower spectrum width.

Jul. 10, 2023
  • Vol. 60 Issue 13 1314001 (2023)
  • Jianlin Chen, and Xuyue Wang

    To minimize the heat-affected zone (HAZ) width in laser-cut carbon fiber composites, the Box-Behnken experimental design was employed using the response surface method to establish a regression equation for the HAZ width at the laser entrance. The effects of laser power, scanning speed, auxiliary gas pressure, focus position, and their interactions on the response surface were investigated. The process parameters were optimized based on the regression equation and actual cutting results. The experimental results show that the laser power, scanning speed, focus position, and auxiliary gas pressure are the most important factors affecting the HAZ width at the laser inlet. The optimal process parameters are a laser power of 170 W, a scanning speed of 1.5 m/min, an auxiliary gas pressure of 0.6 MPa, and a focus on the upper surface of the specimen. The experimental results show that the HAZ width at the laser inlet was 486.13 μm, with an average error of 5.3% for the regression equation.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1314002 (2023)
  • Hao Zhao, Jixin Yang, Xiaoqi Hu, Rui Wang, and Yunjie Bi

    In this study, we developed a numerical model of the coaxial nozzle and powder transport process. Using numerical simulation we examined the effect of different processing parameters on powder convergence in the coaxial nozzle under both vertical and inclined conditions. Our results indicate that an increase in carrier gas velocity leads to a decrease in powder concentration at the powder focusing location, while the velocity of the shielding gas has little effect on the powder concentration. When the carrier gas velocity is 8 L/min, the shielding gas velocity is 20 L/min, and the powder feeding rate is 15.8 g/min, the use of the coaxial nozzle in an inclined position increases the focusing height of the powder from 19 mm to 21 mm and the focus diameter from 3.7 mm to 4.2 mm, compared to that in a vertical position. However, the uniformity of the powder distribution is much better when the coaxial nozzle is used vertically. Our numerical simulation results are consistent with the experimental results and can accurately reflect the powder transportation characteristics under different powder delivery methods.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1314003 (2023)
  • Hao Zhang, Yaqing Hou, Yazhou He, Haohao Kong, Fafa Li, and Hang Su

    Compositionally graded samples were fabricated from pure Fe to Fe20Cr (mass fraction, %) through laser powder bed fusion and in-situ alloying using a blend of Fe and Cr elemental powders as feedstock. The compositional homogeneity, phase structure, microstructure morphology, and microhardness of the component area with different Cr contents were investigated. The results revealed that the gradient composition sample was well alloyed, and the maximum average deviation of all the composition gradients was 0.35%. X-ray diffraction analysis revealed that the composition gradients had a body-centered cubic structure. The microstructure of pure Fe consisted equiaxed grains, and with the increase of Cr content, the transformation from equiaxed to columnar grains occurred between Fe10Cr and Fe12Cr. Furthermore, the grain-boundary strengthening effect of equiaxed grains can effectively enhance the microhardness of the samples, with Fe10Cr having the highest microhardness among all composition gradients at 181 HV0.5.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1314004 (2023)
  • Guangming Tao, Zijian Zheng, Bin Zhu, and Zhijun Ma

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316000 (2023)
  • Yiheng Tang, Yang Weng, Zequn Chen, Xiaojing Li, Ke Si, Wei Gong, Hongtao Lin, and Lan Li

    Optogenetic nanoprobes are an important technique in optogenetics, utilized to deliver precise light stimulation to neurons in organisms, aiding neuroscientists in investigating the working mechanisms of the brain. Optogenetic nanoprobes have the potential to be used in the diagnosis and treatment of neurological disorders. To fulfill stimulation requirements such as stimulation intensity, stimulation range, stimulation patterns, and temporal and spatial resolution, researchers have developed probes capable of performing various optical functions. To fulfill functional requirements such as in-situ electrophysiological recording and delivery of chemical or biological molecules, scientists have developed multi-functional probes. In order to overcome the disadvantages of traditional optoelectronic devices, as they are rigid and easy to cause severe damage to organisms, flexible optical neural probes have been invented. This type of probe causes minimal harm to the organism during implantation and maintains a consistent level of light illumination, ensuring a prolonged life span. This paper provides an overview and the prospects for different types and functions of optogenetic probes, as well as their flexible technologies.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316001 (2023)
  • Jingjing Guo, Xiaoyan Guo, Jialin Tuo, Zhuozhou Li, and Lijun Xu

    With the intense exploration of photonic materials and devices in emerging fields such as wearable techniques, smart healthcare, and biomimetic robotics, developing photonic devices with high flexibility, biocompatibility, and even biodegradability has become critical. To obtain photonic devices with outstanding optical and biomechanical properties, research and development on various aspects, including material synthesis, structural design, function implementation, and device fabrication, are urgent. Organic polymers have been considered to be some of the most competitive materials for flexible photonics due to their soft texture, flexibility, biocompatibility, facile synthesis, and simple modification. A series of novel functional photonic devices such as optical waveguides, diffraction gratings, and photonic crystals, have been developed based on organic polymers. This paper provides a comprehensive review of recent progress on the study of flexible organic polymer photonics. Current techniques, methods, and applications are summarized and analyzed. Perspectives on the future challenges and applications of flexible photonics are also discussed.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316002 (2023)
  • Cheng Zhang, Xiaoyu Wen, Jun Xu, Xuehui Ma, Yutong Ye, Yingjie Ma, Yucong Zhou, and Yitong Li

    A fiber optic fabric sensor for respiratory monitoring of smart clothing is investigated. The sensor consists of a multilayer composite of a stretch-sensitive optical fiber, thermoplastic polyurethane elastomer (TPU), and an elastic fabric. A heating-based sizing method for the multibending cascade structure of polymer optical fibers is proposed to prepare stretch-sensitive optical fibers with precise characteristic dimensions. Using the TPU material, the bonding of stretch-sensitive optical fibers, TPU material, and fabric is realized by ironing to form a laminated fabric sensor. The prepared fabric sensor has no bubbles and wrinkles between the layers, has good production repeatability, and can be connected with garments without sewing to enhance their comfort and aesthetics. Experiments show that the sensor has a strain coefficient of up to 71.01, a stretch rate of up to 83%, a hysteresis error of <12%, and a unidirectional stretch-sensing capability. The designed respiration monitoring sample garment is put through its paces, and the measurements revealed that it is capable of capturing a clear respiration waveform under a variety of breathing frequencies, wearer postures, and movement states. The maximum error of respiration rate is <2 times/min and the average error is within 0.8 times/min.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316003 (2023)
  • Gaoming Jiang, Chaoyu Chen, Lijun Chen, and Pibo Ma

    Optoelectronic techniques have developed rapidly in recent years and play a crucial role in various fields, particularly energy harvesting and sensing. The smart wearable device has also gained widespread acceptance by the market as the next hotspot of smart terminal industry. In order to fabricate intelligent wearable devices, optoelectronic techniques will inevitably become more prevalent in textile industry. The advantages of textile material, including flexibility, wearability, and mature processing technology, make it an excellent carrier of intelligent electronic devices. Based on optoelectronic techniques, intelligent textiles can achieve a variety of additional functions, such as sensing, energy harvesting, and interaction. Therefore, this paper summarizes the classification, development, and application of smart wearable textiles based on optoelectronic techniques, which can better integrate with traditional textile structure and technology, thereby promoting the development of smart textiles in various fields.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316004 (2023)
  • Anping Yang, Hongyou Zhou, Jie Fang, Sijie Su, Xiangyang Song, Ziqi Huang, and Jiulin Gan

    A flexible fluorescent fiber temperature sensor doped with upconversion fluorescent nanoparticles based on fluorescence intensity ratio (FIR) technology is proposed to improve the stability and anti-interference of contact flexible fiber temperature sensor. The composite flexible fiber doped with rare earth ions emits stable fluorescence when excited, and the intensity of the central fluorescence peak corresponding to the thermal coupling energy level of upconversion nanoparticles follows the changes of temperature. The proposed flexible fiber temperature sensor mainly uses the ratio of the center fluorescence peak intensity corresponding to the thermal coupling energy level of the doped Er3+ after FIR treatment as the characterization value. Its temperature response is thermally enhanced which means the fluorescence intensity is enhanced with the increase of temperature. The experimental results show that the proposed sensor exhibits high stability and strong anti-interference, as well as good flexibility and deformation capability, high sensitivity and repeatability. The maximum absolute sensitivity and the maximum relative sensitivity are 0.0038 ℃-1 and 1.29 %/℃, respectively.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316005 (2023)
  • Xiran Du, Xueyang Wang, and Bin Zhu

    In a hot environment, personal cooling is important to maintain thermal comfort. In recent years, radiative cooling textiles can enhance the heat dissipation of the human body through the design of the infrared optical properties without consuming energy, which provides a new opportunity for realizing personal cooling in indoor and outdoor environments. Unlike the indoor controllable thermal environment, the outdoor thermal environment is characterized by strong solar irradiance intensity. Therefore, it is necessary to prevent the input of solar heat while enhancing human body heat dissipation. Based on the difference between indoor and outdoor thermal environments, we introduce the design strategy of radiative cooling textiles from the perspective of indoor and outdoor application scenarios, summarize the recent progress of radiative cooling textiles, and prospect the future development.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316006 (2023)
  • Dechun Zou, and Lü Zhibin

    All-solid-state fiber solar cell is one of the key technologies for the practical application of fiber-shaped photovoltaic cells. This study reviews the development history of the optical structure of fiber-shaped photovoltaic cells, focusing on the innovation and importance of the two-electrode winding structure design adopted in fiber-shaped photovoltaic cells without transparent conductive oxides. The application of new materials, such as non-fullerene-based organic molecules and perovskites, and new preparation processes for the optically active layers, such as the vapor-assisted deposition method, have led to breakthroughs in the research of all-solid-state fiber solar cells that achieve photoelectric conversion efficiencies of 10% to 16%. However, there are still significant challenges in the modularization of all-solid-state fiber batteries. In the future, fiber-shaped photovoltaic cells for wearable devices will need to integrate new materials and processes to develop recyclable, high-performance, environmentally-friendly, and weave-integrated all-solid-state fiber photovoltaic cells.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316007 (2023)
  • Long Qin, Yunci Wang, and Siwei Xiang

    Fiber-structured electronic devices were attractive subjects in recent years, but fiber-structured photoelectrode, as their core component, has not been mass-manufactured. Particularly, there is always a contradiction between long-term stable preservation of precursor sol and rapidly controllable deposition of local gel in the process of assembling common semiconductor oxides such as ZnO nanostructured along long-size fiber electrodes. Therefore, an electrodeposition method was developed, which is suitable for continuous and controllable deposition of nano ZnO on long fiber-shaped substrate. A miniature continuous flow reactor capable of moving along long fibers was designed, meanwhile, the micelle migration was enhanced by electrophoresis, so as to trigger the rapid gelation of the sol on local fiber electrode. Finally, the nano ZnO thin layer was uniformly coated on the metal-plated polymer fiber with more than 1 m in length. Besides, the ZnO layer with porous structure and nanorod array structure were further grown. Thus, a series of fiber structure ZnO-based photoelectrode materials were developed. It has been successfully applied to fiber solar cells, and the best device has achieved an open circuit voltage of 0.446 V, a short circuit current density of 3.77 mA·cm-2, and a fill factor of 0.41. The proposed method provides an important idea for breaking through the bottleneck of mass production of various fiber-structured oxide semiconductor electrodes and realizing scalable processing of fabric electronic devices and intelligent textile.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316008 (2023)
  • Mengjia Chen, Fuguang Chen, Zhi Chen, Meilin Gong, Xiaofeng Liu, and Zhijun Ma

    With a unique type of luminescence, mechanoluminescent materials have begun drawing increasing research interest. In particular, due to high efficiency of energy conversion of mechanical force to light emission, low mechanoluminescence threshold, and recoverable mechanoluminescent property, materials with elastic mechanoluminescence have demonstrated great application potential in stress monitoring, self-powered sensing, biological health monitoring, and smart wearables, among others. Mechanoluminescent optical fibers simultaneously possess the mechanoluminescent property and the advantages of optical fibers, such as the wave guiding function, small size, low weight, high flexibility, and excellent integrability. Compared with the bulky and film-shaped materials, mechanoluminescent optical fibers can convert stress or strain into light emission more efficiently owing to their fibrous shape. Moreover, mechanoluminescent optical fibers can perform the collection and long-distance transmission of mechanoluminescence signals through their wave-guiding structure, thus further expanding their application range. In this short review, we first briefly introduce the classification, characteristics, and mechanism of mechanoluminescent materials. Based on this, different kinds of mechanoluminescent optical fibers, their fabrication methods, and potential applications are presented. Finally, we forecast the future development of mechanoluminescent optical fibers.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316009 (2023)
  • Zhe Wang, Wangkai Jiang, Kaichen Xu, and Xiaoqiao Wang

    With rapid development of wearable electronic technology, flexible thermoelectrics have become an important research topic in the field of wearable energy devices, owing to their sustainable power-supply ability, flexibility, and portability. However, the application of flexible thermoelectric devices in wearables is limited by their low stretchability, lack of breathability, and poor functional integration. Fiber-based stretchable thermoelectric devices with one-dimensional structure feature properties such as small size, lightweight, large deformation, and weavability, which make them suitable for integration into wearable fabrics. In addition, these devices can harvest thermal energy from human body. In this study, the materials, structures, and processing techniques developed for the fabrication of stretchable fiber thermoelectric devices are reviewed. Thereafter, their applications in self-powered sensing, energy harvesting, and thermoelectric cooling are discussed. Finally, a summary and an outlook are provided on the development of fiber thermoelectric devices wherein the key challenges of their practical applications are highlighted.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316010 (2023)
  • Zheshan Wang, Liuping Sun, Yan Wang, Jianchen Hu, and Keqin Zhang

    With the growing demand for sustainable, wearable, and clean energy, triboelectric nanogenerator (TENG) has attracted wide attention. Textile-based triboelectric nanogenerator (T-TENG) has the advantages of lightweight, soft, and comfortable wearing, and has been the focus of design and research. Since fiber and yarn are the basic units of textiles, fiber/yarn-based TENG can be prepared into fabrics with different structures or integrated into other fabrics through subsequent processing, which can fully retain the advantages of fabric structure itself. Therefore, the design and development of fiber/yarn-based TENG with excellent performance is considered to be one of the fundamental solutions for the manufacture of T-TENG. This paper introduces the basic principles of TENG, fiber/yarn-based TENG manufacturing technology, and the integrated strategy of fiber/yarn-based TENG. Finally, the challenges and prospects for the preparation of fiber/yarn-based TENG are presented.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316011 (2023)
  • Min Sun, Xu Lu, Gang Yuan, Jinwei Cao, Rongtai Lu, Guowu Tang, Dongdan Chen, and Qi Qian

    With both the properties of bulk thermoelectric material and advantages of flexible fiber structure, thermoelectric fibers are widely applied in energy conversion, thermoelectric cooling, temperature sensing, thermal management, and thermal imaging, and have become a research hotspot in the field of flexible thermoelectric technology. In this review, the concept and characteristics of inorganic micro-nano thermoelectric fibers are firstly introduced. Secondly the chemical and physical fabrication methods for these fibers are outlined. Then, the important properties and applications of micro-nano thermoelectric fibers are compared. Finally, the current research status of micro-nano thermoelectric fibers is summarized and the future development direction is prospected.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316012 (2023)
  • Ming Xiao, Chaoyang Miao, Jing Bian, and Jianmin Li

    Two-dimensional (2D) transition metal carbon/nitride (MXene) is a new group of 2D nanomaterial with excellent electrical, mechanical properties, as well as the rich and tunable surface chemistry, which has received wide attention in functional materials. In addition, MXene can be dispersed in a variety of solvents to form high-concentration dispersions and exhibits nematic liquid crystal properties, which exhibit nematic liquid crystal properties above a critical concentration, allowing for the preparation of macroscopically continuous fiber by wet spinning process. Until now, MXene fibers have exhibited high electrical/thermal conductivity, mechanical strength, and other properties, showing promising potential for the development of the new generation of wearable electronics. This review first introduces MXene materials and their preparation methods, followed by four common methods of fiber spinning. Then, the development of pure MXene fibers and MXene-based composite fibers is summarized. Finally, the possible future directions and challenges of wet-spun MXene-based fibers are concluded, which may provide reference ideas for the future research of MXenes.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316013 (2023)
  • Danyang Feng, Yicheng Xiao, and Zunfeng Liu

    Elastocaloric cooling is a novel refrigeration technology that has remarkable potential in solving of the problems related to current refrigerants and vapor compression refrigeration. This technology has the advantages of environmentally friendly, high efficiency, and energy saving. In addition, elastocaloric cooling ensures optimal costs and better cooling capacity and feasibility. However, the materials used to realize elastocaloric cooling suffer from problems such as large space requirement and low cycle life. Hence, realizing highly efficient and environment-friendly solid-state refrigeration remains a substantial challenge. This study summarizes the principles, types, and device designs related to these cooling materials. First, the basic mechanism and the methods used for the characterization of the elastocaloric effect are introduced. Second, the research progress and problems related to the use of NiTi-based, Cu-based, and Fe-based ferromagnetic shape memory alloys and elastic polymers to realize solid-state cooling are summarized. Finally, the elastocaloric refrigeration devices developed thus far are summarized and discussed herein.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316014 (2023)
  • Yankun Qi, Zhihao Zhang, Lü Shichao, and Shifeng Zhou

    Optogenetics is a technology that integrates optics, genetics, and genetic engineering to accurately control the activity of neurons. With the unique advantages of high spatial, temporal resolution and cell type specificity, optogenetics overcomes many shortcomings of traditional methods to control the activity of cells, and provides a revolutionary research method for the field of neurology. The applications of optogenetics technology are governed by the functional neural probes. In recent years, multifunctional optical fiber probe has attracted much attention due to its photoelectric functional, small size and high biocompatibility. First, the basic functions of optogenetic neural probes, the classification of neural probes and the preparation methods of integrated neural probes are introduced. Second, typical applications of multifunctional optical fiber probes in optogenetics are reviewed. Finally, existing problems and possible solutions of multifunctional optical fiber used in optogenetics are discussed.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316015 (2023)
  • Zhi Chen, Lijing Zhong, Mengjia Chen, Yuying Wang, Xiaofeng Liu, Zhijun Ma, and Jianrong Qiu

    The femtosecond laser direct-writing technique has been extensively explored for fabricating three-dimensional optical waveguide devices in transparent, hard, and fragile materials owing to its ultrashort pulse duration, ultrahigh peak power, high manufacturing precision, and efficiency. Recently, there is a growing interest in producing optical waveguide devices in flexible polydimethylsiloxane (PDMS) using the femtosecond laser direct-writing technique. This study reviewed the latest development in femtosecond laser direct-writing Type-I optical waveguide devices in flexible PDMS, focusing on three aspects: the basic principle of different kinds of optical waveguide written by femtosecond laser; materials design, direct-writing principle, and processing technology of Type-I optical waveguide directly-written by femtosecond laser in flexible PDMS in last five years; and research progress of the application of the optical waveguide devices in flexible PDMS based on femtosecond laser direct-writing technique for diffraction gratings and cochlear endoscope. Finally, herein, the research progress in this field is summarized, analyzed and concluded, and the future research, application, and developmental direction are outlined.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316016 (2023)
  • Jinlei Zhou, Xihu Lei, Benshan Zou, Yingqiang Shen, and Feng Gao

    A series of Si-doped Bi3.79Er0.03Yb0.18Ti2.97W0.03O12∶xSi phosphors were prepared by high temperature solid-state sintering, and their structures and upconversion fluorescence properties were explored. The experimental and test results show that the Bi3.79Er0.03Yb0.18Ti2.97W0.03O12∶xSi phosphors prepared in different atmospheres are Bi4Ti3O12 phase with single layered perovskite like structure. Si is mainly Si4+ in the phosphor, indicating that even in the argon atmosphere, most of the doped Si is oxidized. Si doping increases the density and surface smoothness of the material, reduces the optical band gap and enhances the light absorption. Under 980 nm infrared light excitation, the upconversion emission spectra of all samples show three emission bands centered at 525 nm, 545 nm, and 765 nm, respectively, corresponding to the electronic transitions in the Er3+4f electron layer. The luminescence intensity and fluorescence lifetime of the sample doped with 6% Si mole fraction are about twice as that of the sample without doping Si, indicating that Si doping can significantly improve the photoluminescence performance of rare earth doped bismuth titanate based phosphors

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316017 (2023)
  • Jun Fu, Jiajia Yin, Junming Shao, Bin Fan, Jiang Bian, and Junfeng Du

    Thin film diffractive lens is an important development direction in space lightweight imaging. High-performance polyimide film materials are widely used because of their good comprehensive properties, but their low visible light transmittance and unstable performance in space environments limit their development in the field of substrates for space thin film optical mirrors. In this paper, SiO2 antireflection film was prepared on the surface of the Fresnel diffraction lens by the sol-gel dip-pulling method. This composite structure design improves the visible light transmittance of polyimide film on the one hand, and improves its radiation resistance to space environment through surface silicon dioxide film on the other hand. This study provides a reference for the design and fabrication of space optical thin film diffraction lenses.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316018 (2023)
  • Kexue Sun, Jianglin Li, Zefeng Chen, Jianbin Xu, and Qiang Zhao

    Van der Waals heterojunctions made from two-dimensional materials offer competitive opportunities for designing and implementing multifunctional and high-performance electronic and optoelectronic devices. A pentagonal two-dimensional-layered noble metal transition metal disulfide molecular complex PdSe2 is used to construct a heterojunction capable of operating at room temperature, which has air stability and high electron field-effect mobility. InSe devices manufactured on rigid SiO2/Si substrates have a response time of approximately 50 ms, exhibiting long-term stability in optical switches, and can be performed on flexible substrates. Under the appropriate band alignment design of the Schottky junction and heterojunction, the heterostructure comprising PdSe2 and InSe exhibits a high reverse rectification ratio exceeding 106, ultralow forward current lower than pA at room temperature, and a high current on/off ratio exceeding 108. Therefore, the PdSe2/InSe van der Waals heterojunction can be used as an ultrasensitive photodetector, exhibiting apparent photovoltaic effects and spectral detection capability. This study provides a new approach to van der Waals integration and design based on two-dimensional materials and energy band alignment technology for photoelectric multifunctional equipment.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316019 (2023)
  • Mengjie Wang, Fei Wang, Chengshuang Zhang, Caizhi Jin, Yanling Bao, Chenghao Zhang, Dong Liu, Jing Wu, and Zhongmin Su

    In order to clarify the melting and solidification characteristics of CF/PEEK irradiated by a flat top laser, the mathematical model of the square flat top laser beam and the geometric model of CF/PEEK composites are constructed in this paper. The heating process of the square flat top laser irradiated CF/PEEK and the cooling process after the heating is stopped are calculated and simulated using the COMSOL finite element simulation software. The square flat top laser power density is 5 MW/m, and the power ratio of the flat top area is 94.37%. The surface temperature of CF/PEEK reaches about 370 ℃ after heating for 15 ms. The temperature difference within the irradiation area along the axial direction of carbon fiber is within 0.5 ℃, and the temperature difference at the edge of the irradiation area is about 1 ℃. The temperature curve in the irradiation area along the radial direction of the carbon fiber is wavy, with the temperature difference between the wave crest and the wave trough of 4 ℃, and the temperature difference at the edge of the irradiation area of about 5 ℃. In CF/PEEK solidification process, there will be small molten pool area and large solid-liquid coexistence area.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316020 (2023)
  • Shuhan Chen, Xiaochun Liu, Lina Wang, and Jue Gong

    The energy loss in the process of hot carrier relaxation is the main factor limiting the further improvement of the efficiency of solar cells. In recent years, researchers have proposed the concept of photovoltaic devices based on the energy utilization of hot carriers, aiming at collecting and utilizing the energy of hot carriers before they relax to the edge of the energy band. Compared with traditional semiconductors, perovskite materials have a slower hot carrier relaxation rate and have the potential to realize hot-carrier solar cells. This review first introduces the main structures of hot carrier solar cells, then summarizes the research progress of perovskite materials in the hot carrier relaxation process and effective extraction, and discusses the current suitable hot carrier extraction materials. Finally, the development direction of perovskite materials in hot carrier solar cells is prospected.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316021 (2023)
  • Rui Wang, Shuilan Wang, Xingchen Jiang, Dehua Cheng, and Qin Dai

    In this study, the heat distributions of MgO∶PPLN crystals under different incident pump optical radii are simulated and analyzed. Considering the temperature rise phenomenon near the central axis of the crystal during operation, the crystal heating parameter t is added to optimize the crystal temperature tuning curve. The inverse conversion phenomenon of MgO∶PPLN optical parametric oscillation (OPO) is experimentally analyzed. Furthermore, the relationship between the parametric light reflectance of the cavity mirror and the optimal pump super-threshold multiple is investigated, and the effect of crystal length on the OPO conversion efficiency is analyzed. By optimizing the experiments, the continuous change range of the signal light wavelength in the temperature range of 30-190 °C is measured to be 1568.9-1659.8 nm. At a pump power of 1.12 W, repetition frequency of 15 kHz, and temperature of 90 °C, the obtained near-infrared laser output is 1595 nm with a maximum average power of 110 mW.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316022 (2023)
  • Haihua Wu, Zhi Liu, Qiang Zhong, Yi Kang, Zenghui Yang, Heng Wei, Jiahuan Hao, and Yunxin Ji

    In this paper, based on the principle of micro-hot pressing additive manufacturing technology, rapid preparation of graphite silicon carbide ceramic composites is achieved, using natural flake graphite powder as the raw material and thermosetting phenolic resin as the adhesive. Particular focus is placed on the composition of mixed powder, and how this affects its compressive strength and thermal conductivity. The results show that when the natural flake graphite powder and the thermosetting phenolic resin is fixed at 85% and 15%, respectively, the mass fractions of high purity silica powder, short carbon fiber, and intermediate carbon microspheres is 25%, 4% and 21%, respectively. The compressive strength and thermal conductivity of the graphite silicon carbide ceramic composite is 30.82 MPa and 21.65 W/m·K, respectively. By testing the thermal expansion coefficient and oxidation resistance of the composite at 1200 ℃, the oxidation weight loss and the thermal expansion coefficient is determined to be 23.679% and 3.14×10-6/K, respectively. This composite material is expected to replace graphite casting and be applied in the casting industry.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1316023 (2023)
  • Tao Liu, Xingxin Cheng, Zigang Zhou, and Yongjia Yang

    We propose a tunable terahertz broadband absorber based on circular and L-shaped couplings. Its main structure is composed of an electrically tunable graphene material at the top, a dielectric material SiO2 in the middle, and gold at the bottom. The absorption spectra of this device are studied using the COMSOL software and the multiple reflection interference theory. The results show that the simulated and theoretical absorption spectra significantly overlap. On the premise of keeping the slit, changing the shape of the central graphene will not change the performance of the absorber. When the Fermi energy level of graphene is regulated to 0.95 eV by an applied voltage, the device is polarization independent and exhibits a strong absorption of more than 90% with a spectral width of more than 4.1 THz. This study will therefore have potential applications in optical switching, modulators, and energy harvesting, and it will provide further inspiration for the design of terahertz broadband absorbers.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1323001 (2023)
  • Shihang Chen, Li Liu, Zhiwei Deng, Zhongqi Hao, Jiulin Shi, and Xingdao He

    The extremely low Ta and Nb content in tantalum-niobium ores affects the sensitivity of conventional laser-induced breakdown spectroscopy (LIBS) techniques. Although the double-pulse LIBS technique offers a significantly improved analytical sensitivity, it suffers from a high equipment cost. Therefore, a double-pulse laser-induced breakdown spectroscopy (DP-LIBS) technique based on a single laser beam splitting configuration is proposed for the high-sensitivity detection of Ta and Nb elements in tantalum-niobium ores. A quantitative LIBS analysis model is developed based on the optimization of experimental parameters such as the distance from the focal point, acquisition delay, and laser energy. The results show that the proposed DP-LIBS system enhances the intensity of the characteristic spectral lines of the Ta and Nb elements by 3-4 times compared with single-pulse LIBS, and increases the detection sensitivity by approximately 2 times, where the detection limits of the Ta and Nb elements are 195.91 μg·g-1 and 81.79 μg·g-1, respectively. Therefore, the proposed technique is a promising method for the rapid and highly-sensitive quantitative analysis of trace elements of Ta and Nb in tantalum-niobium ores.

    Jul. 10, 2023
  • Vol. 60 Issue 13 1330001 (2023)
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