Phase-matching quantum-key distribution(PM-QKD)has achieved significant results in various practical applications.However,real-time communication requires dynamic adjustment and optimization of key parameters during c...Phase-matching quantum-key distribution(PM-QKD)has achieved significant results in various practical applications.However,real-time communication requires dynamic adjustment and optimization of key parameters during communication.In this letter,we predict the PM-QKD parameters using nature-inspired algorithms(NIAs).The results are obtained from an exhaustive traversal algorithm(ETA),which serves as a benchmark.We mainly study the parameter optimization effects of the two NIAs:ant colony optimization(ACO)and the genetic algorithm(GA).The configuration of the inherent parameters of these algorithms in the decoy-state PM-QKD is also discussed.The simulation results indicate that the parameters obtained by the ACO exhibit superior convergence and stability,whereas the GA results are relatively scattered.Nevertheless,more than 97%of the key rates predicted by both algorithms are highly consistent with the optimal key rate.Moreover,the relative error of the key rates remained below 10%.Furthermore,NIAs maintain power consumption below 8 W and require three orders of magnitude less computing time than ETA.展开更多
The band alignment between silicon and high-k dielectrics,which is a key factor in device operation and reliability,still suffers from uncontrolled fluctuations and ambiguous understanding.In this study,by conducting ...The band alignment between silicon and high-k dielectrics,which is a key factor in device operation and reliability,still suffers from uncontrolled fluctuations and ambiguous understanding.In this study,by conducting atomic-level ab initio calculations on realistic Si/SiO_(2)/HfO_(2)stacks,we reveal the physical origin of band alignment fluctuations,i.e.,the oxygen density-dependent interface and surface dipoles,and demonstrate that band offsets can be tuned without introducing other materials.This is instructive for reducing the gate tunneling current,alleviating device-to-device variation,and tuning the threshold voltage.Additionally,this study indicates that significant attention should be focused on model construction in emerging atomistic studies on semiconductor devices.展开更多
We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element ...We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.展开更多
We propose a fully symmetrical QKD system that enables quantum states to be prepared and measured simultaneously without compromising system performance.Over a 25.6 km fiber channel,we demonstrate point-to-point QKD o...We propose a fully symmetrical QKD system that enables quantum states to be prepared and measured simultaneously without compromising system performance.Over a 25.6 km fiber channel,we demonstrate point-to-point QKD operations with asymmetric Mach–Zehnder interferometer modules.Two interference visibilities of above99%indicate that the proposed system has excellent stability.Consequently,the scheme not only improves the feasibility of distributing secret keys,but also enables QKD closer to more practical applications.展开更多
The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Proce...The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems.Polarization Division Multiplexed Quadrature Phase Shift Keying(PDM-QPSK)is deployed to reach high bit rates,provides modified digital clock recovery,and allows BER-Aided Constant Modulus Algorithm(BA-CMA)equalising.A Soft Decision-Forward Error Correction(SD-FEC)algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance.A compact coherent transceiver is also developed.These techniques have been applied in the largest 100 G Optical Transport Network(OTN)deployment in the world,the backbone expansion project for Phase 3 of the China Education and Research Network(CERNET),with a total transmission length of 10 000 km.展开更多
This paper presents a constructive discussion and inclusive review on advancements in the coded modulation free-space optical(FSO) communication system and corresponding techniques. These techniques mainly include cha...This paper presents a constructive discussion and inclusive review on advancements in the coded modulation free-space optical(FSO) communication system and corresponding techniques. These techniques mainly include channel model,forward error correction(FEC) and modulation schemes. Firstly,a complete view of FSO system is presented which contains the description,the current research situation along with the advantages over the traditional radio frequency(RF) wireless communication and fiber optical communications. Then,the channel model,FEC,modulation schemes and complete system of coded modulation FSO are analyzed successively. At last,the review work of coded modulation FSO system is summarized and further improvements are prospected.展开更多
As interest in double perovskites is growing,especially in applications like photovoltaic devices,understanding their mechanical properties is vital for device durability.Despite extensive exploration of structure and...As interest in double perovskites is growing,especially in applications like photovoltaic devices,understanding their mechanical properties is vital for device durability.Despite extensive exploration of structure and optical properties,research on mechanical aspects is limited.This article builds a vacancyordered double perovskite model,employing first-principles calculations to analyze mechanical,bonding,electronic,and optical properties.Results show Cs_(2)Hfl_(6),Cs_(2)SnBr_(6),Cs_(2)SnI_(6),and Cs_(2)PtBr_(6)have Young's moduli below 13 GPa,indicating flexibility.Geometric parameters explain flexibility variations with the changes of B and X site composition.Bonding characteristic exploration reveals the influence of B and X site electronegativity on mechanical strength.Cs_(2)SnBr_(6)and Cs_(2)PtBr_(6)are suitable for solar cells,while Cs_(2)HfI_(6)and Cs_(2)TiCl_(6)show potential for semi-transparent solar cells.Optical property calculations highlight the high light absorption coefficients of up to 3.5×10^(5) cm^(-1)for Cs_(2)HfI_(6)and Cs_(2)TiCl_(6).Solar cell simulation shows Cs_(2)PtBr_(6)achieves 22.4%of conversion effciency.Cs_(2)ZrCl_(6)holds promise for ionizing radiation detection with its 3.68 eV bandgap and high absorption coefficient.Vacancy-ordered double perovskites offer superior flexibility,providing valuable insights for designing stable and flexible devices.This understanding enhances the development of functional devices based on these perovskites,especially for applications requiring high stability and flexibility.展开更多
A spectrum efficient OFDM scheme named Time Domain Synchronous-OFDM(TDS-OFDM)is introduced into coherent optical transmission system,in which the pseudo noise(PN)sequence is exploited as guard interval to realize fram...A spectrum efficient OFDM scheme named Time Domain Synchronous-OFDM(TDS-OFDM)is introduced into coherent optical transmission system,in which the pseudo noise(PN)sequence is exploited as guard interval to realize frame synchronization,compensate the carrier frequency offset(CFO),and estimate and equalize channel simultaneously.Since there is no pilot signals or training symbols in TDS-OFDM,the proposed scheme can achieve higher spectral efficiency(SE)above 10%improvement comparing with CPOFDM.The proposed method is implemented and verified in a 28GBaud QPSK OFDM system and a 28GBaud 16QAM OFDM system.It is demonstrated that the proposed scheme shows high CFO estimation accuracy and synchronous accuracy.Under CFO and linewidth of laser source set as 100MHz and 100kHz respectively,BER of QPSK OFDM system is below 3.8e-3 at the optical signal-to-noise ratio(OSNR)of 13dB,and BER of 16QAM OFDM system is below 3.8e-3 at the OSNR of 20dB.展开更多
First-principles method is used to simulate the stable structure and optical properties of a 96-atom fused silica.The preferable structure of NBOHC-E＇（non-bridging oxygen hole center（NBOHC） and E＇ center） pair d...First-principles method is used to simulate the stable structure and optical properties of a 96-atom fused silica.The preferable structure of NBOHC-E＇（non-bridging oxygen hole center（NBOHC） and E＇ center） pair defect is predicted to be located at 2.4 A^° for the Si-O bond length.The quasi-particle GOWO calculations are performed and an accurate band gap is obtained in order to calculate the optical absorption properties.With the stretching of the Sil-O1 bond,an obvious redshift can be observed in the absorption spectrum.In the case of NBOHC-E＇ pair,the p-orbital DOS of Si1 atom will shift to the conduction band.Two obvious absorption peaks can be observed in the absorption spectrum.The calculation reproduced the peak positions of the well-known optical absorption bands.展开更多
We propose a novel two-dimensional photonic crystal structure consisting of two line defect waveguides and a cavity to realize mode conversion based on the coupling effect. The W1/cavity/W2 structure breaks the spatia...We propose a novel two-dimensional photonic crystal structure consisting of two line defect waveguides and a cavity to realize mode conversion based on the coupling effect. The W1/cavity/W2 structure breaks the spatial symmetry and successfully converts the even（odd） mode to the odd（even） mode in the W2 waveguide during the forward（backward）transmission. When considering the incidence of only the even mode, the optical diode effect emerges and achieves approximate 35 d B unidirectionality at the resonant frequency. Moreover, owing to the narrow bandpass feature and the flexibility of the tuning cavity, utilization of the proposed structure as a wavelength filter is demonstrated in a device with a Y-branch splitter. Here, we provide a heuristic design for a mode converter, optical diode, and wavelength filter derived from the coupling effect between a cavity and adjacent waveguides, and expect that the proposed structure can be applied as a building block in future all-optical integrated circuits.展开更多
Q-switched lasers have occupied important roles in industrial applications such as laser marking,engraving,welding,and cutting due to their advantages in high pulse energy.Here,SnS_(2)-based Q-switched lasers are impl...Q-switched lasers have occupied important roles in industrial applications such as laser marking,engraving,welding,and cutting due to their advantages in high pulse energy.Here,SnS_(2)-based Q-switched lasers are implemented.Consid-ering that SnS_(2) inherits the thickness sensitive optical characteristics of TMD,three kinds of SnS2 with different thick-ness are characterized in terms of nonlinearity and used to realize the Q-switched pulses under consistent implementa-tion conditions for comparison tests.According to the results,the influence of thickness variation on the nonlinear per-formance of saturable absorber,such as modulation depth and absorption intensity,and the influence on the correspond-ing laser are analyzed.In addition,compared with other traditional saturable absorbers,the advantage of SnS_(2) in realiz-ing ultrashort pulses is also noticed.Our work explores the thickness-dependent nonlinear optical properties of SnS_(2),and the rules found is of great reference value for the establishment of target lasers.展开更多
In this paper, we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration. A segment of 10-m photonic crystal fiber with a high nonlinear coefficient ...In this paper, we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration. A segment of 10-m photonic crystal fiber with a high nonlinear coefficient of 62.8 W-1/kin is utilized to realize large scale soliton self-frequency shift relevant to the power of the sampled optical signal. Furthermore, a 100-m dispersion-increasing fiber is used as the spectral compression module for further resolution enhancement. Simulation results show that 317-nm maximum wavelength shift is realized with 1550-nm initial wavelength and 6-bit quantization resolution is obtained with a subsequent spectral compression process.展开更多
In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift(SSFS)and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber(PCF) is ...In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift(SSFS)and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber(PCF) is used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10m-long dispersion flattened hybrid cladding hexagonal-octagonal PCF(6/8-PCF) is utilized as a spectral compression medium to further enhance the resolution. Simulation results show that 6-bit quantization resolution is still obtained when a 100m-long dispersion-increasing fiber(DIF)is replaced by a 6/8-PCF in spectral compression module.展开更多
In free space channel,continuous-variable quantum key distribution(CV-QKD)using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization n...In free space channel,continuous-variable quantum key distribution(CV-QKD)using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization non-sensitive of the free-space channel,but also reduce the noise introduced by phase interference.However,arbitrary continuous modulation can not be carried out in the past polarization coding,resulting in that the signal state can not obtain arbitrary continuous value in Poincare space,and the security analysis of CV-QKD using polarized coherent-states in free space is not complete.Here we propose a new modulation method to extend the modulation range of signal states with an optical-fiber-based polarization controller.In particular,in terms of the main influence factors in the free-space channel,we utilize the beam extinction and elliptical model when considering the transmittance and adopt the formulation of secret key rate.In addition,the performance of the proposed scheme under foggy weather is also taken into consideration to reveal the influence of severe weather.Numerical simulation shows that the proposed scheme is seriously affected by attenuation under foggy weather.The protocol fails when visibility is less than 1 km.At the same time,the wavelength can affect the performance of the proposed scheme.Specifically,under foggy weather,the longer the wavelength,the smaller the attenuation coefficient,and the better the transmission performance.Our proposed scheme can expand the modulation range of signal state,and supplement the security research of the scheme in the free-space channel,thus can provide theoretical support for subsequent experiments.展开更多
Flat supercontinuum in the telecommunication wave bands of E+S+C is generated by coupling a train of femtosecond pulses generated by a mode-locked Ti:sapphire laser into the fundameutal mode of a photonic crystal fibe...Flat supercontinuum in the telecommunication wave bands of E+S+C is generated by coupling a train of femtosecond pulses generated by a mode-locked Ti:sapphire laser into the fundameutal mode of a photonic crystal fiber with central holes fabricated in our lab. The pulse experiences the anomalous dispersion regime,and the soliton dynamic effect plays an important role in supercontinuum generation.The output spectrum in the wavelength range of 1360 1565nm does not include significant ripples due to higher pump peak power,and the normalized intensity shows less fluctuation.展开更多
For a long time,optical and wireless systems/net-works are developed in separate communities witha few attempts for in-depth convergence.In fact,it prom-ises many advantages to combine the optical and wire-less techno...For a long time,optical and wireless systems/net-works are developed in separate communities witha few attempts for in-depth convergence.In fact,it prom-ises many advantages to combine the optical and wire-less technologies in the levels of systems and networks.Recently,both academia and industry have made manyefforts to enter a new phase of development to take op-tical and wireless systems as fully integrated networks.To provide high bandwidth and reliable service for bothfixed and mobile users,a well-designed network展开更多
The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are st...The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing（CO-OFDM）system and the single carrier（SC） PDM quadrature phase shift keying（QPSK） system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.展开更多
A novel trellis coded-4×8 overlapping amplitude and pulse position modulation(TC-4×8AOPPM) scheme is proposed to enhance bit error rate(BER) performance of free-space optical communication(FSO) system. In ad...A novel trellis coded-4×8 overlapping amplitude and pulse position modulation(TC-4×8AOPPM) scheme is proposed to enhance bit error rate(BER) performance of free-space optical communication(FSO) system. In addition, an uncoded AOPPM referential scheme is also designed. The schemes manage to decrease BER by designing gamma-gamma(GG) channel applicable decoding and demodulation methods. Simulation results of 8, 16 and 64-state TC-4×8AOPPM show 2.5-3.3 dB SNR gain against traditional TC-4×8AOPPM scheme respectively. Thus significant BER performance improvement is achieved and the reliability of the FSO system is also enhanced.展开更多
Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in re...Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.展开更多
A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetr...A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure.By using the full-vector finite element method,the propagation characteristics of the proposed DC-PCF PBS are investigated.The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm,which covers the S+C+L+U communication bands,the shortest splitting length is 1.97 mm,and the maximum extinction ratio appears near wavelength 1550 nm.Moreover,the insertion loss of the proposed DC-PCF PBS is very low.It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.展开更多
基金supported by the State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications)No.IPOC2021ZT10BUPT Excellent Ph.D.Students Foundation(Grant No.CX2023207)the BUPT innovation and entrepreneurship support program No.2024-YC-A188。
文摘Phase-matching quantum-key distribution(PM-QKD)has achieved significant results in various practical applications.However,real-time communication requires dynamic adjustment and optimization of key parameters during communication.In this letter,we predict the PM-QKD parameters using nature-inspired algorithms(NIAs).The results are obtained from an exhaustive traversal algorithm(ETA),which serves as a benchmark.We mainly study the parameter optimization effects of the two NIAs:ant colony optimization(ACO)and the genetic algorithm(GA).The configuration of the inherent parameters of these algorithms in the decoy-state PM-QKD is also discussed.The simulation results indicate that the parameters obtained by the ACO exhibit superior convergence and stability,whereas the GA results are relatively scattered.Nevertheless,more than 97%of the key rates predicted by both algorithms are highly consistent with the optimal key rate.Moreover,the relative error of the key rates remained below 10%.Furthermore,NIAs maintain power consumption below 8 W and require three orders of magnitude less computing time than ETA.
基金supported by the National Natural Science Foundation of China(Grant Nos.62174155,12334005,and T2293702)the CAS Project for Young Scientists in Basic Research(Grant No.YSBR-056)the MIND Project(Grant No.MINDKT202403)。
文摘The band alignment between silicon and high-k dielectrics,which is a key factor in device operation and reliability,still suffers from uncontrolled fluctuations and ambiguous understanding.In this study,by conducting atomic-level ab initio calculations on realistic Si/SiO_(2)/HfO_(2)stacks,we reveal the physical origin of band alignment fluctuations,i.e.,the oxygen density-dependent interface and surface dipoles,and demonstrate that band offsets can be tuned without introducing other materials.This is instructive for reducing the gate tunneling current,alleviating device-to-device variation,and tuning the threshold voltage.Additionally,this study indicates that significant attention should be focused on model construction in emerging atomistic studies on semiconductor devices.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60908028, 60971068, 10979065, and 61275201)the Fundamental Research Funds for the Central Universities of China (Grant Nos. 2011RC0402 and 2012RC0402)the Program for New Century Excellent Talents in University of China (Grant No. NCET-10-0261)
文摘We investigate the effect of disorder and mechanical deformation on a two-dimensional photonic crystal waveguide. The dispersion characteristics and transmittance of the waveguide are studied using the finite element method. Results show that the geometric change of the dielectric material perpendicular to the light propagation direction has a larger influence on the waveguide characteristics than that parallel to the light propagation direction. Mechanical deformation has an obvious influence on the performance of the waveguide. In particular, longitudinal deformed structure exhibits distinct optical characteristics from the ideal one. Studies on this work will provide useful guideline to the fabrication and practical applications based on photonic crystal waveguides.
基金Supported by the Fundamental Research Funds for the Central Universities(Grant No.2019XD-A02)the State Key Laboratory of Information Photonics and Optical Communications,Beijing University of Posts and Telecommunications(Grant No.IPO2019ZT06)。
文摘We propose a fully symmetrical QKD system that enables quantum states to be prepared and measured simultaneously without compromising system performance.Over a 25.6 km fiber channel,we demonstrate point-to-point QKD operations with asymmetric Mach–Zehnder interferometer modules.Two interference visibilities of above99%indicate that the proposed system has excellent stability.Consequently,the scheme not only improves the feasibility of distributing secret keys,but also enables QKD closer to more practical applications.
基金supported by the National Natural Science Foundation of China under Grant No. 60932004the National High Technical Research and Development Program of China (863 Program) under Grants No. 2012AA011301,No. 2012AA011303
文摘The explosive increase in data traffic requires networks to provide higher capacity and long-haul transmission capabilities.This paper introduces new results on high-order modulation and efficient Digital Signal Processing algorithms to reduce various transmission limitations in coherent receiving systems.Polarization Division Multiplexed Quadrature Phase Shift Keying(PDM-QPSK)is deployed to reach high bit rates,provides modified digital clock recovery,and allows BER-Aided Constant Modulus Algorithm(BA-CMA)equalising.A Soft Decision-Forward Error Correction(SD-FEC)algorithm and a joint scheme with timing recovery and adaptive equaliser are used to achieve better performance.A compact coherent transceiver is also developed.These techniques have been applied in the largest 100 G Optical Transport Network(OTN)deployment in the world,the backbone expansion project for Phase 3 of the China Education and Research Network(CERNET),with a total transmission length of 10 000 km.
基金supported in part by the National NSFC with No. 61425022National High Technology 863 Program of China with No. 2013AA013403+5 种基金National Basic Research Program of China with No. 2010CB328300National NSFC (No. 60932004,61275074,61275158,& 61201151)National International Technology Cooperation with No.2012DFG1210Universities Ph.D. Special Research Funds with No. 20120005120007Beijing Excellent Ph.D. Thesis Guidance Foundation with No. 20121001302Open foundation of state key laboratory of optical communication technologies and networks(WRI)
文摘This paper presents a constructive discussion and inclusive review on advancements in the coded modulation free-space optical(FSO) communication system and corresponding techniques. These techniques mainly include channel model,forward error correction(FEC) and modulation schemes. Firstly,a complete view of FSO system is presented which contains the description,the current research situation along with the advantages over the traditional radio frequency(RF) wireless communication and fiber optical communications. Then,the channel model,FEC,modulation schemes and complete system of coded modulation FSO are analyzed successively. At last,the review work of coded modulation FSO system is summarized and further improvements are prospected.
基金supported by the National Natural Science Foundation of China(62305261,62305262)the Natural Science Foundation of Shaanxi Province(2024JC-YBMS-021,2024JC-YBMS-788,2023-JC-YB-065,2023-JC-QN-0693,2022JQ-652)+1 种基金the Xi’an Science and Technology Bureau of University Service Enterprise Project(23GXFW0043)the Cross disciplinary Research and Cultivation Project of Xi’an University of Architecture and Technology(2023JCPY-17)。
文摘As interest in double perovskites is growing,especially in applications like photovoltaic devices,understanding their mechanical properties is vital for device durability.Despite extensive exploration of structure and optical properties,research on mechanical aspects is limited.This article builds a vacancyordered double perovskite model,employing first-principles calculations to analyze mechanical,bonding,electronic,and optical properties.Results show Cs_(2)Hfl_(6),Cs_(2)SnBr_(6),Cs_(2)SnI_(6),and Cs_(2)PtBr_(6)have Young's moduli below 13 GPa,indicating flexibility.Geometric parameters explain flexibility variations with the changes of B and X site composition.Bonding characteristic exploration reveals the influence of B and X site electronegativity on mechanical strength.Cs_(2)SnBr_(6)and Cs_(2)PtBr_(6)are suitable for solar cells,while Cs_(2)HfI_(6)and Cs_(2)TiCl_(6)show potential for semi-transparent solar cells.Optical property calculations highlight the high light absorption coefficients of up to 3.5×10^(5) cm^(-1)for Cs_(2)HfI_(6)and Cs_(2)TiCl_(6).Solar cell simulation shows Cs_(2)PtBr_(6)achieves 22.4%of conversion effciency.Cs_(2)ZrCl_(6)holds promise for ionizing radiation detection with its 3.68 eV bandgap and high absorption coefficient.Vacancy-ordered double perovskites offer superior flexibility,providing valuable insights for designing stable and flexible devices.This understanding enhances the development of functional devices based on these perovskites,especially for applications requiring high stability and flexibility.
基金supported by the State Grid Corporation of China (No. 5101/2017-3205A)the Open Fund of the Guangdong Provincial Key Laboratory of Optical Fiber Sensing and Communications (Jinan University)the National Natural Science Foundation of China (NSFC) (61571057, 61501214, 61527820, 61575082)
文摘A spectrum efficient OFDM scheme named Time Domain Synchronous-OFDM(TDS-OFDM)is introduced into coherent optical transmission system,in which the pseudo noise(PN)sequence is exploited as guard interval to realize frame synchronization,compensate the carrier frequency offset(CFO),and estimate and equalize channel simultaneously.Since there is no pilot signals or training symbols in TDS-OFDM,the proposed scheme can achieve higher spectral efficiency(SE)above 10%improvement comparing with CPOFDM.The proposed method is implemented and verified in a 28GBaud QPSK OFDM system and a 28GBaud 16QAM OFDM system.It is demonstrated that the proposed scheme shows high CFO estimation accuracy and synchronous accuracy.Under CFO and linewidth of laser source set as 100MHz and 100kHz respectively,BER of QPSK OFDM system is below 3.8e-3 at the optical signal-to-noise ratio(OSNR)of 13dB,and BER of 16QAM OFDM system is below 3.8e-3 at the OSNR of 20dB.
基金supported by the National Basic Research Program of China(Grant No.2014CB643900)the Open Fund of IPOC(BUPT)+2 种基金the Open Program of State Key Laboratory of Functional Materials for Informaticsthe National Natural Science Foundation for Theoretical Physics Special Fund “Cooperation Program”(Grant No.11547039)Shaanxi Provincial Institute of Scientific Research Plan Projects,China(Grant No.SLGKYQD2-05)
文摘First-principles method is used to simulate the stable structure and optical properties of a 96-atom fused silica.The preferable structure of NBOHC-E＇（non-bridging oxygen hole center（NBOHC） and E＇ center） pair defect is predicted to be located at 2.4 A^° for the Si-O bond length.The quasi-particle GOWO calculations are performed and an accurate band gap is obtained in order to calculate the optical absorption properties.With the stretching of the Sil-O1 bond,an obvious redshift can be observed in the absorption spectrum.In the case of NBOHC-E＇ pair,the p-orbital DOS of Si1 atom will shift to the conduction band.Two obvious absorption peaks can be observed in the absorption spectrum.The calculation reproduced the peak positions of the well-known optical absorption bands.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61372037 and 61307069)Beijing Excellent Ph.D. Thesis Guidance Foundation,China(Grant No.20131001301)the Natural Science Foundation of Shanxi Province,China(Grant No.2013021017-3)
文摘We propose a novel two-dimensional photonic crystal structure consisting of two line defect waveguides and a cavity to realize mode conversion based on the coupling effect. The W1/cavity/W2 structure breaks the spatial symmetry and successfully converts the even（odd） mode to the odd（even） mode in the W2 waveguide during the forward（backward）transmission. When considering the incidence of only the even mode, the optical diode effect emerges and achieves approximate 35 d B unidirectionality at the resonant frequency. Moreover, owing to the narrow bandpass feature and the flexibility of the tuning cavity, utilization of the proposed structure as a wavelength filter is demonstrated in a device with a Y-branch splitter. Here, we provide a heuristic design for a mode converter, optical diode, and wavelength filter derived from the coupling effect between a cavity and adjacent waveguides, and expect that the proposed structure can be applied as a building block in future all-optical integrated circuits.
基金the financial support from the National Natural Science Foundation of China(11875008,12075034)Open Research Fund of State Key Laboratory of Pulsed Power Laser Technology(Grant SKL2019KF04)Fundamental Research Funds for the Central Universities(2019XD-A09-3).
文摘Q-switched lasers have occupied important roles in industrial applications such as laser marking,engraving,welding,and cutting due to their advantages in high pulse energy.Here,SnS_(2)-based Q-switched lasers are implemented.Consid-ering that SnS_(2) inherits the thickness sensitive optical characteristics of TMD,three kinds of SnS2 with different thick-ness are characterized in terms of nonlinearity and used to realize the Q-switched pulses under consistent implementa-tion conditions for comparison tests.According to the results,the influence of thickness variation on the nonlinear per-formance of saturable absorber,such as modulation depth and absorption intensity,and the influence on the correspond-ing laser are analyzed.In addition,compared with other traditional saturable absorbers,the advantage of SnS_(2) in realiz-ing ultrashort pulses is also noticed.Our work explores the thickness-dependent nonlinear optical properties of SnS_(2),and the rules found is of great reference value for the establishment of target lasers.
基金Project supported by the National Basic Research Program of China(Grant Nos.2010CB327605 and 2010CB328304)the National High-Technology Research and Development Program of China(Grant No.2013AA031501)+7 种基金the National Natural Science Foundation of China(Grant No.61307109)the Research Foundation from Ministry of Education of China(Grant No.109015)the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NECT-11-0596)the Beijing Nova Program,China(Grant No.2011066)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20120005120021)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.2013RC1202)the China Postdoctoral Science Foundation(Grant No.2012M511826)the Postdoctoral Science Foundation of Guangdong Province,China(Grant No.244331)
文摘In this paper, we propose an optical quantization scheme for all-optical analog-to-digital conversion that facilitates photonics integration. A segment of 10-m photonic crystal fiber with a high nonlinear coefficient of 62.8 W-1/kin is utilized to realize large scale soliton self-frequency shift relevant to the power of the sampled optical signal. Furthermore, a 100-m dispersion-increasing fiber is used as the spectral compression module for further resolution enhancement. Simulation results show that 317-nm maximum wavelength shift is realized with 1550-nm initial wavelength and 6-bit quantization resolution is obtained with a subsequent spectral compression process.
文摘In this paper, we optimize a proposed all-optical quantization scheme based on soliton self-frequency shift(SSFS)and pre-chirp spectral compression techniques. A 10m-long high-nonlinear photonic crystal fiber(PCF) is used as an SSFS medium relevant to the power of the sampled optical pulses. Furthermore, a 10m-long dispersion flattened hybrid cladding hexagonal-octagonal PCF(6/8-PCF) is utilized as a spectral compression medium to further enhance the resolution. Simulation results show that 6-bit quantization resolution is still obtained when a 100m-long dispersion-increasing fiber(DIF)is replaced by a 6/8-PCF in spectral compression module.
基金the Key Program of the National Natural Science Foundation of China(Grant No.61531003)the National Natural Science Foundation of China(Grant No.62001041)+1 种基金China Postdoctoral Science Foundation(Grant No.2020TQ0016)the Fund of State Key Laboratory of Information Photonics and Optical Communications.
文摘In free space channel,continuous-variable quantum key distribution(CV-QKD)using polarized coherent-states can not only make the signal state more stable and less susceptible to interference based on the polarization non-sensitive of the free-space channel,but also reduce the noise introduced by phase interference.However,arbitrary continuous modulation can not be carried out in the past polarization coding,resulting in that the signal state can not obtain arbitrary continuous value in Poincare space,and the security analysis of CV-QKD using polarized coherent-states in free space is not complete.Here we propose a new modulation method to extend the modulation range of signal states with an optical-fiber-based polarization controller.In particular,in terms of the main influence factors in the free-space channel,we utilize the beam extinction and elliptical model when considering the transmittance and adopt the formulation of secret key rate.In addition,the performance of the proposed scheme under foggy weather is also taken into consideration to reveal the influence of severe weather.Numerical simulation shows that the proposed scheme is seriously affected by attenuation under foggy weather.The protocol fails when visibility is less than 1 km.At the same time,the wavelength can affect the performance of the proposed scheme.Specifically,under foggy weather,the longer the wavelength,the smaller the attenuation coefficient,and the better the transmission performance.Our proposed scheme can expand the modulation range of signal state,and supplement the security research of the scheme in the free-space channel,thus can provide theoretical support for subsequent experiments.
基金Supported by the Key Program of the National Natural Science Foundation of China under Grant No 60637010the National Basic Research Program of China under Grant Nos 2010CB327604 and 2010CB327604Qinhuangdao Science and Technology Research and Development Program under Grant No 201101A093.
文摘Flat supercontinuum in the telecommunication wave bands of E+S+C is generated by coupling a train of femtosecond pulses generated by a mode-locked Ti:sapphire laser into the fundameutal mode of a photonic crystal fiber with central holes fabricated in our lab. The pulse experiences the anomalous dispersion regime,and the soliton dynamic effect plays an important role in supercontinuum generation.The output spectrum in the wavelength range of 1360 1565nm does not include significant ripples due to higher pump peak power,and the normalized intensity shows less fluctuation.
文摘For a long time,optical and wireless systems/net-works are developed in separate communities witha few attempts for in-depth convergence.In fact,it prom-ises many advantages to combine the optical and wire-less technologies in the levels of systems and networks.Recently,both academia and industry have made manyefforts to enter a new phase of development to take op-tical and wireless systems as fully integrated networks.To provide high bandwidth and reliable service for bothfixed and mobile users,a well-designed network
基金supported by the National Natural Science Foundation of China(Grant Nos.61271192,61427813,and 61331010)the National Basic Research Program of China(Grant No.2013AA013401)
文摘The compensation effects of fiber nonlinearity in 112 Gb/s polarization division multiplexing（PDM） coherent optical systems by mid-span optical phase conjugation（OPC） based on four wave mixing（FWM） effect are studied. Comparisons of the compensation results between PDM coherent optical-orthogonal frequency division multiplexing（CO-OFDM）system and the single carrier（SC） PDM quadrature phase shift keying（QPSK） system are provided as well. The results demonstrate that nonlinear compensation effect with mid-span OPC in PDM CO-OFDM system is much more obvious than that in SC PDM QPSK system.
基金supported in part by the National NSFC with No.61425022National High Technology 863 Program of China with No.2013AA013403+5 种基金National Basic Research Program of China with No.2010CB328300National NSFC(No.60932004,61275074,61275158,& 61201151)National International Technology Cooperation with No.2012DFG12110Universities Ph.D. Special Research Funds with No.20120005120007Beijing Excellent Ph.D. Thesis Guidance Foundation with No. 20121001302Open foundation of state key laboratory of optical communication technologies and networks(WRI)
文摘A novel trellis coded-4×8 overlapping amplitude and pulse position modulation(TC-4×8AOPPM) scheme is proposed to enhance bit error rate(BER) performance of free-space optical communication(FSO) system. In addition, an uncoded AOPPM referential scheme is also designed. The schemes manage to decrease BER by designing gamma-gamma(GG) channel applicable decoding and demodulation methods. Simulation results of 8, 16 and 64-state TC-4×8AOPPM show 2.5-3.3 dB SNR gain against traditional TC-4×8AOPPM scheme respectively. Thus significant BER performance improvement is achieved and the reliability of the FSO system is also enhanced.
基金Project supported by the Scientific Fund for Chinese Universities (Grant No. BUPT 2011RC009)
文摘Real time phase regeneration is necessary for degraded phase modulation format optical communication systems. A regenerator based on the discrimitive gain effect of a semiconductor optical amplifier was proposed in recent years. In this paper, for this type of regenerator, its optimal working condition is found by solving the dynamic equations which describe the variance of the optical field and carrier density in the semiconductor optical amplifier by the finite difference method. The results show that the optimal improvement of signal Q factor can reach more than 2.2 dB.
基金Project supported by the National Key Research and Development Project of China(Grant No.2019YFB2204001)。
文摘A novel polarization beam splitter(PBS)based on dual-core photonic crystal fiber(DC-PCF)is proposed in this work.The proposed DC-PCF PBS contains two kinds of lattices and three kinds of air holes to form the asymmetrical elliptic dual-core structure.By using the full-vector finite element method,the propagation characteristics of the proposed DC-PCF PBS are investigated.The simulation results show that the bandwidth of the proposed DC-PCF PBS can reach to 340 nm,which covers the S+C+L+U communication bands,the shortest splitting length is 1.97 mm,and the maximum extinction ratio appears near wavelength 1550 nm.Moreover,the insertion loss of the proposed DC-PCF PBS is very low.It is believed that the proposed DC-PCF PBS has important applications in the field of all-optical communication and network.
