This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design(CL-ACRWA),which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical ...This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design(CL-ACRWA),which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.展开更多
Rare-earth(RE)doping is one of the valid approaches to optimize the optical performance of the CsPbBr_(3)perovskite.However,the underlying mechanism and the role of the RE_4f electrons are still unknown,which are sign...Rare-earth(RE)doping is one of the valid approaches to optimize the optical performance of the CsPbBr_(3)perovskite.However,the underlying mechanism and the role of the RE_4f electrons are still unknown,which are significant for the development of advanced RE-doped perovskite materials.Considering these,a series of CsPbBr_(3):RE(RE=Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb)compounds were studied by applying first-principles calculations.Based on the analysis of the phase stability diagram,we found that RE doping in the bulk CsPbBr_(3)leads to the formation of the REPb defect.Meanwhile,the two types of electric-dipole allowed transition were revealed by exploring the electronic structure.We also demonstrated that the doped systems retain the defect tolerance nature of the host and the RE_4f electrons enrich the band-edge states,which are the main origins for luminescence enhancement.Our current contribution not only presents physical insight into the role of RE_4f electrons in luminescence,but also provides a guideline for designing the targeted RE-doped perovskites.展开更多
Hybrid perovskite nanocrystals(NCs)are widely used in various applications,due to their desirable optoelectronic characteristics.However,the related applications are usually hindered by their poor long-term stability....Hybrid perovskite nanocrystals(NCs)are widely used in various applications,due to their desirable optoelectronic characteristics.However,the related applications are usually hindered by their poor long-term stability.In this work,we have synthesized one kind of CH_(3)NH_(3)PbBr_(3)(MAPbBr_(3))NC that is heteroepitaxially grown with an MA_(1-x)Cs_(x)PbBr_(3) shell,with the aim to optimize the optical properties of the former.It is found that the MAPbBr_(3)/MA_(1-x)Cs_(x)PbBr_(3) core/shell NCs possess optimized optical stability.Through the measurement of the temperature-dependent photoluminescence spectrum,it is confirmed that the core/shell NCs exhibit weaker electron-phonon coupling strength and larger exciton binding energy than the bare MAPbBr_(3) NCs.Interestingly,the core/shell NCs display significantly prolonged biexciton Auger lifetime and enlarged two-photon absorption.Impressively,two-photon pumped amplified stimulated emission is only observed in the core/shell NCs but not in the bare NCs,enabling the former to be promising for application in nonlinear optoelectronic devices.展开更多
The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,an...The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.展开更多
A novel low-complexity framework for designing survivable optical mesh networks with undetermined topology is presented. By jointly optimizing the topology planning, working- and spare-capacity planning, a cost saving...A novel low-complexity framework for designing survivable optical mesh networks with undetermined topology is presented. By jointly optimizing the topology planning, working- and spare-capacity planning, a cost saving of over 40% can be achieved for a national-scale network with 31 nodes.展开更多
A new electro-optical device using Si/SiGe-system with two parallel ridge waveguides is proposed for optical switching and the optimization of the structure for a single mode operation is investigated.
Satellite constellation design for space optical systems is essentially a multiple-objective optimization problem. In this work, to tackle this challenge, we first categorize the performance metrics of the space optic...Satellite constellation design for space optical systems is essentially a multiple-objective optimization problem. In this work, to tackle this challenge, we first categorize the performance metrics of the space optical system by taking into account the system tasks（i.e., target detection and tracking）. We then propose a new non-dominated sorting genetic algorithm（NSGA） to maximize the system surveillance performance. Pareto optimal sets are employed to deal with the conflicts due to the presence of multiple cost functions. Simulation results verify the validity and the improved performance of the proposed technique over benchmark methods.展开更多
Selective absorptive nanofluid can pre-absorb certain sunlight wavelength that cannot be used by PV and transmits remaining sunlight to the surface of PV,which can decouple PV from the thermal receiver spatially.In or...Selective absorptive nanofluid can pre-absorb certain sunlight wavelength that cannot be used by PV and transmits remaining sunlight to the surface of PV,which can decouple PV from the thermal receiver spatially.In order to improve the harvesting of electricity and high-temperature thermal nanofluid,it is important to design an optimal optical filter window(transmit sunlight with wavelengths of 732-1067 nm to the surface of the photovoltaic cell and absorb the remaining sunlight).However,designing optimal optical filter is facing following challenges:(1) inherently narrow selective absorptivity property of single nanoparticle;(2) simplified numerical calculation method calculating transmittance;(3) ignoring the shape of the nanoparticle.In this study,the idea of using multiple nanoparticles coupling effect to design an optical filter is proposed,which can superimpose the narrow absorption bandwidth of different nanoparticles to obtain a wide absorption bandwidth of the whole system.In addition,an improved transmission method considering light-matter interaction at air/vessel and liquid/vessel interfaces is adopted to compute the transmittance.The results calculated by improved transmission method are more accurate than widely used traditional Lambert-Beer law,which is verified by experimental test.Furthermore,the effect of nanoparticle shape on spectral transmittance is also investigated,which shows that spiny Ag can approximately extend absorbance from 400 nm to 600 nm compared to nanosphere silver.Finally,the results show that optical filter efficiency of nanofluids with multiple nanoparticles coupling(Ag,spiny Ag,ZnO,ITO) can reached up to 35%.展开更多
A single-mode optical fiber with quadratic curve index profile in core layer is introduced. The profile is optimized at 850 ran wavelength. The 850 nm bandwidth of this fiber can reach up to 2056.35 MHz.km. This fiber...A single-mode optical fiber with quadratic curve index profile in core layer is introduced. The profile is optimized at 850 ran wavelength. The 850 nm bandwidth of this fiber can reach up to 2056.35 MHz.km. This fiber can be used at 850 nm, 1310 nm, and 1550 nm wavelength.展开更多
An antireflection （AR） coating is fabricated by applying an optimal spin-coating method and a pH-modified SiO2 nanoparticle solution on a cover glass. Because the pH value of the solution will affect the aggregation...An antireflection （AR） coating is fabricated by applying an optimal spin-coating method and a pH-modified SiO2 nanoparticle solution on a cover glass. Because the pH value of the solution will affect the aggregation and dispersion of the SiO2 particles, the transmittance of the AR-treated cover glass will be enhanced under optimal fabricated conditions. The experimental results show that an AR coating fabricated by an SiO2 nano- particle solution of pH 11 enhances the transmittance approximately by 3% and 5% under normal and oblique incident conditions, respectively. Furthermore, the AR-treated cover glass exhibits hydrophobicity and shows a 65% enhancement at a contact angle to bare glass.展开更多
Vertical-cavity surface-emitting lasers(VCSELs)are essential in modern optoelectronic systems,driving applications in high-speed optical communications,3D sensing,and LiDAR.While significant progress has been made in ...Vertical-cavity surface-emitting lasers(VCSELs)are essential in modern optoelectronic systems,driving applications in high-speed optical communications,3D sensing,and LiDAR.While significant progress has been made in improving VCSEL performance,the role of cavity geometry in optimizing key optical characteristics remains insufficiently explored.This study systematically examines how distinct cavity geometries—circular,square,D-shaped,mushroom-shaped,and pentagonal—affect both the static and dynamic properties of broad-area VCSELs.We analyze their effects on optical power,multimode behavior,beam profile,spatial coherence,and polarization dynamics.Our results show that breaking the continuous rotational symmetry of the cavity effectively increases gain utilization and power,changes the multimode lasing characteristics,shapes the beam,and modifies the polarization.Notably,the pentagonal VCSEL exhibits more than twice the optical power density of its circular counterpart.It also supports the highest number of modes and the fastest mode dynamics,driven by strong mode interaction.These properties make it a strong candidate for high-speed entropy generation.Mushroom-shaped VCSELs demonstrate high power and low spatial coherence,making them ideal for speckle-free imaging and illumination applications.Meanwhile,D-shaped VCSELs provide the most stable polarization and controllable multimode behavior with high power,showcasing their potential for applications that require stable and low-coherence light sources.This study offers a comprehensive analysis of the impact of cavity geometry on VCSEL performance,which provides insights for optimizing VCSEL designs tailored to diverse applications that require distinct properties with broad applicability to advanced imaging,sensing,optical coherence tomography,high-speed communication,and other photonic technologies.展开更多
In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and signi...In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.展开更多
We propose a broadband fiber optic parametric amplifier（FOPA） based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength（ZDW） by using a selective liquid infiltration technique.The...We propose a broadband fiber optic parametric amplifier（FOPA） based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength（ZDW） by using a selective liquid infiltration technique.The amplifier gain and bandwidth is investigated for a variety of fiber lengths, pump power, and operating wavelengths. It is observed that sufficient peak gains and broader bandwidths can be achieved with a small negative anomalous dispersion（β2≤ 0） and a positive value of the 4th-order dispersion parameter（t β4）around the pump. We can optimize an FOPA with a bandwidth of more than 220 nm around the communications wavelength.展开更多
A(v,k,λ)difference family((v,k,λ)-DF in short)over an abelian group G of order v,is a collection F=(Bi|i∈I}of k-subsets of G,called base blocks,such that any nonzero element of G can be represented in precisely A w...A(v,k,λ)difference family((v,k,λ)-DF in short)over an abelian group G of order v,is a collection F=(Bi|i∈I}of k-subsets of G,called base blocks,such that any nonzero element of G can be represented in precisely A ways as a difference of two elements lying in some base blocks in F.A(v,k,λ)-DDF is a difference family with disjoint blocks.In this paper,by using Weil's theorem on character sum estimates,it is proved that there exists a(p^n,4,1)-DDF,where p=1(rood 12)is a prime number and n≥1.展开更多
The organic solar cell technology has attracted great interests due to its potential of low cost solution process capability. Bulk heterojunction organic solar cells offer a potentially much cheaper alternative way to...The organic solar cell technology has attracted great interests due to its potential of low cost solution process capability. Bulk heterojunction organic solar cells offer a potentially much cheaper alternative way to harness solar energy, and can be made flexible and large area. They can also be made translucent and in different colors. As a result, the inexpensive fabrication process such as solution- process techniques, mechanical flexibility, light weight and visible-light transparency features make organic solar technology attractive for application in new markets, such as smart sensors, power generating window panes, building architecture, greenhouses and outdoor lifestyle, etc. After a brief overview of basics of organic photo- voltaics, the enhancement of semitransparent organic solar cells over the two competing performance indices of power conversion efficiency and transmittance will be discussed.展开更多
基金supported by the National Natural Science Foundation of China(No.61675033,61575026,61675233)National High Technical Research and Development Program of China(No.2015AA015504)
文摘This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design(CL-ACRWA),which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.
基金the financial aid from the National Key Research and Development Program of China(2016YFB0701003)the National Natural Science Foundation of China(21871248 and 21590794)+3 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences(Y201947)the Key Research Program of Frontier Sciences,AS(YZDY-SSW-JSC018)the K.C.Wong Education Foundation(GJTD-2018-09)the Jilin Province Science and Technology Development Plan Project(20180101172JC).
文摘Rare-earth(RE)doping is one of the valid approaches to optimize the optical performance of the CsPbBr_(3)perovskite.However,the underlying mechanism and the role of the RE_4f electrons are still unknown,which are significant for the development of advanced RE-doped perovskite materials.Considering these,a series of CsPbBr_(3):RE(RE=Ce,Pr,Nd,Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb)compounds were studied by applying first-principles calculations.Based on the analysis of the phase stability diagram,we found that RE doping in the bulk CsPbBr_(3)leads to the formation of the REPb defect.Meanwhile,the two types of electric-dipole allowed transition were revealed by exploring the electronic structure.We also demonstrated that the doped systems retain the defect tolerance nature of the host and the RE_4f electrons enrich the band-edge states,which are the main origins for luminescence enhancement.Our current contribution not only presents physical insight into the role of RE_4f electrons in luminescence,but also provides a guideline for designing the targeted RE-doped perovskites.
基金the National Natural Science Foundation of China(62174079)the Guangdong Basic and Applied Basic Research Foundation(2019A1515012094 and 2022A1515011246)+1 种基金the Project of Department of Education of Guangdong Province(2018KTSCX198)the Science and Technology Planning Project of Shenzhen Municipality(JCYJ20190808121211510 and JCYJ20190808142603561).
文摘Hybrid perovskite nanocrystals(NCs)are widely used in various applications,due to their desirable optoelectronic characteristics.However,the related applications are usually hindered by their poor long-term stability.In this work,we have synthesized one kind of CH_(3)NH_(3)PbBr_(3)(MAPbBr_(3))NC that is heteroepitaxially grown with an MA_(1-x)Cs_(x)PbBr_(3) shell,with the aim to optimize the optical properties of the former.It is found that the MAPbBr_(3)/MA_(1-x)Cs_(x)PbBr_(3) core/shell NCs possess optimized optical stability.Through the measurement of the temperature-dependent photoluminescence spectrum,it is confirmed that the core/shell NCs exhibit weaker electron-phonon coupling strength and larger exciton binding energy than the bare MAPbBr_(3) NCs.Interestingly,the core/shell NCs display significantly prolonged biexciton Auger lifetime and enlarged two-photon absorption.Impressively,two-photon pumped amplified stimulated emission is only observed in the core/shell NCs but not in the bare NCs,enabling the former to be promising for application in nonlinear optoelectronic devices.
基金supported in part by the Research and Study Project of Tokai University General Research Organization and by the Grant-in-Aid for Scientific Research Grant Number 20H02838the Universiti Kebangsaan Malaysia for supporting this study through FRGS/1/2017/TK07/UKM/02/9 Grantsupported by the Research Grants Council of Hong Kong,China(Project Number:152093/18E).
文摘The photovoltaic performance of perovskite solar cells(PSCs)can be improved by utilizing efficient front contact.However,it has always been a significant challenge for fabricating high-quality,scalable,controllable,and cost-effective front contact.This study proposes a realistic multi-layer front contact design to realize efficient single-junction PSCs and perovskite/perovskite tandem solar cells(TSCs).As a critical part of the front contact,we prepared a highly compact titanium oxide(TiO2)film by industrially viable Spray Pyrolysis Deposition(SPD),which acts as a potential electron transport layer(ETL)for the fabrication of PSCs.Optimization and reproducibility of the TiO2 ETL were discreetly investigated while fabricating a set of planar PSCs.As the front contact has a significant influence on the optoelectronic properties of PSCs,hence,we investigated the optics and electrical effects of PSCs by three-dimensional(3D)finite-difference time-domain(FDTD)and finite element method(FEM)rigorous simulations.The investigation allows us to compare experimental results with the outcome from simulations.Furthermore,an optimized single-junction PSC is designed to enhance the energy conversion efficiency(ECE)by>30% compared to the planar reference PSC.Finally,the study has been progressed to the realization of all-perovskite TSC that can reach the ECE,exceeding 30%.Detailed guidance for the completion of high-performance PSCs is provided.
文摘A novel low-complexity framework for designing survivable optical mesh networks with undetermined topology is presented. By jointly optimizing the topology planning, working- and spare-capacity planning, a cost saving of over 40% can be achieved for a national-scale network with 31 nodes.
文摘A new electro-optical device using Si/SiGe-system with two parallel ridge waveguides is proposed for optical switching and the optimization of the structure for a single mode operation is investigated.
文摘Satellite constellation design for space optical systems is essentially a multiple-objective optimization problem. In this work, to tackle this challenge, we first categorize the performance metrics of the space optical system by taking into account the system tasks（i.e., target detection and tracking）. We then propose a new non-dominated sorting genetic algorithm（NSGA） to maximize the system surveillance performance. Pareto optimal sets are employed to deal with the conflicts due to the presence of multiple cost functions. Simulation results verify the validity and the improved performance of the proposed technique over benchmark methods.
基金supported by the National Natural Science Foundation of China (Grant No.52076064)the Taishan Scholars of Shandong Province (tsqn 201812105)+1 种基金China Scholarship Council (202106120157)CSC grant for LIANG Huaxu's scholarship of research visiting at Nanyang Technological University, Singapore。
文摘Selective absorptive nanofluid can pre-absorb certain sunlight wavelength that cannot be used by PV and transmits remaining sunlight to the surface of PV,which can decouple PV from the thermal receiver spatially.In order to improve the harvesting of electricity and high-temperature thermal nanofluid,it is important to design an optimal optical filter window(transmit sunlight with wavelengths of 732-1067 nm to the surface of the photovoltaic cell and absorb the remaining sunlight).However,designing optimal optical filter is facing following challenges:(1) inherently narrow selective absorptivity property of single nanoparticle;(2) simplified numerical calculation method calculating transmittance;(3) ignoring the shape of the nanoparticle.In this study,the idea of using multiple nanoparticles coupling effect to design an optical filter is proposed,which can superimpose the narrow absorption bandwidth of different nanoparticles to obtain a wide absorption bandwidth of the whole system.In addition,an improved transmission method considering light-matter interaction at air/vessel and liquid/vessel interfaces is adopted to compute the transmittance.The results calculated by improved transmission method are more accurate than widely used traditional Lambert-Beer law,which is verified by experimental test.Furthermore,the effect of nanoparticle shape on spectral transmittance is also investigated,which shows that spiny Ag can approximately extend absorbance from 400 nm to 600 nm compared to nanosphere silver.Finally,the results show that optical filter efficiency of nanofluids with multiple nanoparticles coupling(Ag,spiny Ag,ZnO,ITO) can reached up to 35%.
文摘A single-mode optical fiber with quadratic curve index profile in core layer is introduced. The profile is optimized at 850 ran wavelength. The 850 nm bandwidth of this fiber can reach up to 2056.35 MHz.km. This fiber can be used at 850 nm, 1310 nm, and 1550 nm wavelength.
基金financially supporting this research under Contract No. NSC 102-2221-E-155-076-MY3
文摘An antireflection （AR） coating is fabricated by applying an optimal spin-coating method and a pH-modified SiO2 nanoparticle solution on a cover glass. Because the pH value of the solution will affect the aggregation and dispersion of the SiO2 particles, the transmittance of the AR-treated cover glass will be enhanced under optimal fabricated conditions. The experimental results show that an AR coating fabricated by an SiO2 nano- particle solution of pH 11 enhances the transmittance approximately by 3% and 5% under normal and oblique incident conditions, respectively. Furthermore, the AR-treated cover glass exhibits hydrophobicity and shows a 65% enhancement at a contact angle to bare glass.
基金supported by the King Abdullah University of Science and Technology(KAUST)under the Grant of Transition Award in Semiconductors:Grant No.FCC/1/5939the KAUST Center of Excellence for Renewable Energy and Storage Technologies(CREST):Grant No.FCC/1/5937the KAUST Grant Nos.RFS-OFP2023-5534,BAS/1/1614-01-01,ORA-2022-5313,and ORFS-2022-CRG11-5079.
文摘Vertical-cavity surface-emitting lasers(VCSELs)are essential in modern optoelectronic systems,driving applications in high-speed optical communications,3D sensing,and LiDAR.While significant progress has been made in improving VCSEL performance,the role of cavity geometry in optimizing key optical characteristics remains insufficiently explored.This study systematically examines how distinct cavity geometries—circular,square,D-shaped,mushroom-shaped,and pentagonal—affect both the static and dynamic properties of broad-area VCSELs.We analyze their effects on optical power,multimode behavior,beam profile,spatial coherence,and polarization dynamics.Our results show that breaking the continuous rotational symmetry of the cavity effectively increases gain utilization and power,changes the multimode lasing characteristics,shapes the beam,and modifies the polarization.Notably,the pentagonal VCSEL exhibits more than twice the optical power density of its circular counterpart.It also supports the highest number of modes and the fastest mode dynamics,driven by strong mode interaction.These properties make it a strong candidate for high-speed entropy generation.Mushroom-shaped VCSELs demonstrate high power and low spatial coherence,making them ideal for speckle-free imaging and illumination applications.Meanwhile,D-shaped VCSELs provide the most stable polarization and controllable multimode behavior with high power,showcasing their potential for applications that require stable and low-coherence light sources.This study offers a comprehensive analysis of the impact of cavity geometry on VCSEL performance,which provides insights for optimizing VCSEL designs tailored to diverse applications that require distinct properties with broad applicability to advanced imaging,sensing,optical coherence tomography,high-speed communication,and other photonic technologies.
基金supported by the Distinguish Young Scholars of the National Natural Science Foundation of China(Grant No. 52225601)the Major Program of the National Natural Science Foundation of China(Grant No.52090061)。
文摘In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber tube.These limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.
基金the Science&Engineering ResearchBoard(SERB),New Delhi,India,for the NPDF fellowship(File No.PDF/2016/001827)support received from NationalInstitute of Science Education and Research(NISER),Department of Atomic Energy(DAE),Government of India
文摘We propose a broadband fiber optic parametric amplifier（FOPA） based on a near-zero ultra-flat dispersion profile with a single zero-dispersion wavelength（ZDW） by using a selective liquid infiltration technique.The amplifier gain and bandwidth is investigated for a variety of fiber lengths, pump power, and operating wavelengths. It is observed that sufficient peak gains and broader bandwidths can be achieved with a small negative anomalous dispersion（β2≤ 0） and a positive value of the 4th-order dispersion parameter（t β4）around the pump. We can optimize an FOPA with a bandwidth of more than 220 nm around the communications wavelength.
基金Supported by the National Natural Science Foundation of China(No.10561002)Guangxi Science Foundation(No.0640062)Innovation Project of Guangxi Graduate Education.
文摘A(v,k,λ)difference family((v,k,λ)-DF in short)over an abelian group G of order v,is a collection F=(Bi|i∈I}of k-subsets of G,called base blocks,such that any nonzero element of G can be represented in precisely A ways as a difference of two elements lying in some base blocks in F.A(v,k,λ)-DDF is a difference family with disjoint blocks.In this paper,by using Weil's theorem on character sum estimates,it is proved that there exists a(p^n,4,1)-DDF,where p=1(rood 12)is a prime number and n≥1.
文摘The organic solar cell technology has attracted great interests due to its potential of low cost solution process capability. Bulk heterojunction organic solar cells offer a potentially much cheaper alternative way to harness solar energy, and can be made flexible and large area. They can also be made translucent and in different colors. As a result, the inexpensive fabrication process such as solution- process techniques, mechanical flexibility, light weight and visible-light transparency features make organic solar technology attractive for application in new markets, such as smart sensors, power generating window panes, building architecture, greenhouses and outdoor lifestyle, etc. After a brief overview of basics of organic photo- voltaics, the enhancement of semitransparent organic solar cells over the two competing performance indices of power conversion efficiency and transmittance will be discussed.
