The polarization switching（PS） and polarization bistability（PB） characteristics of a 1550-nm vertical-cavity surfaceemitting laser（VCSEL） subjected to orthogonal optical injection are systematically investigated...The polarization switching（PS） and polarization bistability（PB） characteristics of a 1550-nm vertical-cavity surfaceemitting laser（VCSEL） subjected to orthogonal optical injection are systematically investigated.The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power.The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS.In the case of forward scanning injected power,with the increase of frequency detuning level between the VCSEL and the injected light,the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning.In the case of reversely scanning injected power,the injected power required for PS displays fluctuant changes within the whole frequency detuning range.Specifically,PS may disappear under certain negative frequency detuning and large bias current.Furthermore,the hysteresis width as a function of the frequency detuning is calculated,and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning.展开更多
Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a...Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.展开更多
This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd：YAG lasers. Under optical feedback, the polarization state of longitu...This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd：YAG lasers. Under optical feedback, the polarization state of longitudinal modes in quasi-isotropic lasers relies strongly on the intracavity anisotropy loss and mode competition. When the intracavity anisotropy loss is small, external optical feedback can cause polarization switching and strong mode competition between two orthogonal linearly polarized eigenstates of one laser longitudinal mode, which leads to the distortion of laser intensity modulation waveform. The polarization switching is independent of the initial external cavity length. By increasing the intracavity anisotropy loss, one polarization eigenstate can be suppressed and the laser works in single-polarization state. A theoretical analysis based on the compound cavity model is presented, which is in good agreement with the experimental results. The results offer guidance to the development of laser feedback interferometers.展开更多
The research of high-performance polarization controllers is of great significance for expanding the application field of polarization optics. Here, a polarization switch is demonstrated by using a dual-core photonic ...The research of high-performance polarization controllers is of great significance for expanding the application field of polarization optics. Here, a polarization switch is demonstrated by using a dual-core photonic crystal fiber(DCPCF)with four symmetrical air holes, placed above and below each core, filled with magnetic fluid(MF). The switch, which utilizes a magnetic field to change the coupling length ratio of the x and y polarization modes, enables dynamic tuning of the polarization state and extinction ratio. Numerical results show that when the working length is 36.638 mm, the magneto–optical polarization switch can operate in four communication bands, i.e., 1509 nm to 1520 nm, 1544 nm to1556 nm, 1578 nm to 1591 nm, and 1611 nm to 1624 nm. Moreover, the extinction ratio(ER) is greater than 20 d B in the fiber length range of 38.5 mm to 38.7 mm, indicating that the device has a good fault tolerance for the interception of the fiber length.展开更多
The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric ...The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric fields is discussed.The results show that the FDF is a process of nucleation and growth in ferroelectric without applying any external stress.Four kinds of parallelogram shaped ferroelectric domains are formed at the steady state,in which the 180° anti-phase domains regularly align along the 45° direction and the 90° anti-phase domains regularly distribute like a stepladder.Steady electric fields can rotate domain polarization by 90° and 180°,and force the orientation-favorite domains and the average polarization to grow into larger ones.The greater the steady electric field,the larger the average polarization at the steady state.In ferroelectrics subject to an alternating electric field,domain polarization switches to cause a hysteresis loop and an associated butterfly loop with the alternating electric field.The coercive field and remnant field are enhanced with the increase of the electric field frequency or strength,or with the decrease of temperature.展开更多
Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device.The dependencies of electron spin-polarization on the strip’s...Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device.The dependencies of electron spin-polarization on the strip’s magnetization strength,width and position have been systematically investigated.A novel magnetic control spin-polarization switch is proposed by inserting a ferromagnetic metal(FM)strip eccentric in relation to off the center of the spin filter,which produces the first energy level spin-polarization reversal.It is believed to be of significant importance for the realization of semiconductor spintronics multiple-value logic devices.展开更多
This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fu...This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou＇s eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.展开更多
We perform a theoretical study on the polarization-resolved compound lasing mode （CLM） of two mutually coupled vertical-cavity surface-emitting lasers （VCSELs）. Different solutions of CLMs are derived though stabi...We perform a theoretical study on the polarization-resolved compound lasing mode （CLM） of two mutually coupled vertical-cavity surface-emitting lasers （VCSELs）. Different solutions of CLMs are derived though stability analysis of the spin-flip model. The dynamical evolvements of CLMs with the existence of polarization degrees of freedom are also charactered. The most stable CLM with the smallest carrier density tend to be excited, since the gain needed for this mode to emit is the lowest. In the given system, varying values of injection rate or birefringence, etc., will change the generation of the preferred CLMs in the two polarization directions, and thus influence the polarization switching （PS） characteristics. Thus, hoppings between CLMs are also companied by PSs. Through mapping of average power in the parameter space, the influences of coupling rate and anisotropy parameters （linear dichroism and linear birefringence） on PS and hopping between CLMs are discussed.展开更多
We perform micromagnetic simulations on the switching of magnetic vortex core by using spin-polarized currents through a three-nanocontact geometry. Our simulation results show that the current combination with an app...We perform micromagnetic simulations on the switching of magnetic vortex core by using spin-polarized currents through a three-nanocontact geometry. Our simulation results show that the current combination with an appropriate current flow direction destroys the symmetry of the total effective energy of the system so that the vortex core can be easier to excite,resulting in less critical current density and a faster switching process. Besides its fundamental significance, our findings provide an additional route to incorporating magnetic vortex phenomena into data storage devices.展开更多
Achieving simultaneous polarization and spin switching at room temperature is essential for advanced multi-state storage and control applications,particularly in magnetoelectrics and electron spintronics,yet such mate...Achieving simultaneous polarization and spin switching at room temperature is essential for advanced multi-state storage and control applications,particularly in magnetoelectrics and electron spintronics,yet such materials are exceedingly rare.Based on polar molecular valence tautomerism of Co^(Ⅲ)(3,5-DBcat)(3,5-DBsq)(trans-4-stypy)_(2)(1),room-temperature spin and polarization switching was achieved via electron transfer.Notably,the ferroelectric polarization and spin switching in 1 are modulated by both temperature and light.The successful implementation of room-temperature polarization and spin switching in 1 signifies an important advancement toward practical applications.展开更多
In a chaotic system of vertical cavity surface emitting laser （VCSEL） with external optical-injection, we propose a novel implementation scheme for reconfigurable dynamic all-optical chaotic logic operations （AOCLO...In a chaotic system of vertical cavity surface emitting laser （VCSEL） with external optical-injection, we propose a novel implementation scheme for reconfigurable dynamic all-optical chaotic logic operations （AOCLOs）. Under different key parameters, such as the bias current, the injection strength and the frequency detuning of the injected light field and the VCSEL, we also explore the evolutions of the polarization-bistability with the amplitude of the injected light field when the output of VCSEL is chaotic wave. According to the dynamic evolutions, we find out the optimal value of the frequency detuning that is considered as a control logic signal, and further implement different AOCLOs, such as AND, NAND, OR, NOR, XOR, and XNOR, by controlling the logic operation of the control logic signal between two logic inputs. Moreover, the ability to reconstruct these logic operations is demonstrated under relatively low noise strength of the spontaneous emission.展开更多
Nonlinear electro-mechanical behaviors of piezoelectric materials and viscoelastic nature of polymers result in the overall nonlinear and hysteretic responses of active polymeric composites. This study presents a hybr...Nonlinear electro-mechanical behaviors of piezoelectric materials and viscoelastic nature of polymers result in the overall nonlinear and hysteretic responses of active polymeric composites. This study presents a hybrid-unit-cell model for obtaining the effective nonlinear and rate-dependent hysteretic electro-mechanical responses of hybrid piezocomposites. The studied hybrid piezocomposites consist of unidirectional piezoelectric fibers embedded in a polymeric matrix, which is reinforced with piezoelectric particles. The hybrid-unit-cell model is derived based on a unit-cell model of fiber-reinforced composites consisting of fiber and matrix subcells, in which the matrix subcells are comprised of a unit-cell model of particle-reinforced composites. Nonlinear electro-mechanical responses are considered for the piezoelectric constituents while a viscoelastic solid constitutive model is used for the polymer constituent. The hybrid-unit cell model is used to examine the effects of different responses of the constituents, microstructural arrangements, and loading histories on the overall nonlinear and hysteretic electro-mechanical responses of the hybrid piezocomposites, which are useful in designing active polymeric composites.展开更多
HfO_(2)-based ferroelectricfilms have been extensively explored and utilized in thefield of non-volatile memory and electrical programmability.However,the trade-off between ferroelectric polarization and dielectric co...HfO_(2)-based ferroelectricfilms have been extensively explored and utilized in thefield of non-volatile memory and electrical programmability.However,the trade-off between ferroelectric polarization and dielectric constant in HfO_(2)has limited the overall performance improvement of devices in practical applications.Herein,a novel approach is proposed for the Hf_(0.5)Zr_(0.5)O_(2)/ZrO_(2)(HZO/ZrO_(2))nanobilayer engineering,which can effectively regulate the phase structure evolution of HfO_(2)films to construct a suitable morphotropic phase boundary(MPB).Thefindings highlight that the top ZrO_(2)layer can regularly promote the formation of either the ferroelectric o-phase or the antiferroelectric t-phase.An ideal MPB is successfully established in HZO/ZrO_(2)(6/9 nm)nanobilayerfilm by carefully optimizing the HZO/ZrO_(2)thickness ratio,which presents a high dielectric constant of 52.7 and a large 2Pr value of up to 72.3 mC/cm^(2)without any wake-up operation.Moreover,the HZO/ZrO2 nanobilayer thinfilms demonstrate faster polarization switching speed(1.09μs)and better fatigue performance(10^(9)cycles)compared to the conventional HZO solid solutionfilms.The relationship between ferroelectric and dielectric properties can be harmoniously balanced through the designation.The results indicate that the HZO/ZrO_(2)nanobilayer engineering strategy is quite potential to pave the way for the development of nextgeneration memory technologies with superior performance and reliability.展开更多
Macroscopic polarization switching achieved through directional electron transfer or spin crossover(SCO)has attracted considerable attention because of its potential applications in data storage devices,sensors,and en...Macroscopic polarization switching achieved through directional electron transfer or spin crossover(SCO)has attracted considerable attention because of its potential applications in data storage devices,sensors,and energy converters.Here,by substituting the central metal and anion of a reported compound,[Fe(RR-cth)Co(SS-cth)(μ-dhbq)](AsF_(6))_(3),we obtained two dinuclear compounds that crystallize in the polar space group,P2_(1),[Fe(RR-cth)Ga(SS-cth)(μ-dhbq)](X)_(3)(X=AsF_(6)and ClO_(4)).Among them,complex 1(AsF_(6))_(3)exhibited a two-step magnetic transition,including SCO behavior near 50 K and a gradual valence tautomerism(VT)behavior that occurred over a wide temperature range up to at least 250 K.The SCO behavior of complex 1(AsF_(6))_(3)can be triggered by changes in temperature or the application of magnetic fields,leading to a polarization change of approximately 0.5μC cm^(−2).The transition entropy of 55.9 J K^(−1)mol^(−1)during the SCO process was obtained using the Clausius-Clapeyron equation.Contrarily,complex 1(ClO_(4))_(3)only exhibited gradual VT behavior from a low temperature to room temperature.Single-crystal X-ray diffraction,variable-temperature infrared spectroscopy,and pyroelectric measurements confirmed the gradual VT process that occurs over a wide temperature range in both complexes.This study broadens the range of polarization switching molecular systems by replacing the central metal and anion,thereby facilitating the development of multifunctional molecular materials.展开更多
Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition bypro...Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.展开更多
Silicon waveguides typically exhibit optical anisotropy,which leads to polarization correlation and single-polarization operations.This consequently creates a demand for polarization-control devices.This paper introdu...Silicon waveguides typically exhibit optical anisotropy,which leads to polarization correlation and single-polarization operations.This consequently creates a demand for polarization-control devices.This paper introduces a CMOS-compatible O-band reconfigurable TE/TM polarization rotator comprising two symmetrical polarization rotator-splitters and phase shifters.This configuration enables dynamic conversion of any linear polarization to its quadratic equivalent.Experimental results indicate that the reconfigurable polarization rotator exhibits an insertion loss of less than 1.5 dB.Furthermore,the bandwidth for a polarization extinction ratio beyond 15 dB exceeds 60 nm.展开更多
Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this wo...Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this work,we study the effects of orientation on the tunneling electroresistance(TER)of ferroelectric tunnel junctions(FTJs).Rhombohedral Pb(Zr_(0.7),Ti_(0.3))O_(3)(PZT)that has the polar axis along the(111)orientation is adopted as potential barriers and two kinds of FTJs that are composed of(001)-and(II1)-oriented PZT barriers and Nb:SrTiO_(3)(Nb:STO)electrodes,respectively,are fabricated.The(111)-oriented P1PZT/Nb:STO FTJ exhibits a giant ON/OFFratio of~1.9×10^(5),about 30 times that of the(001)-oriented device,due to the lowered PZT barrier in the ON state and the widen Schottky barrier in the OFF state based on current and capacitance analyses.In addition,compared to the(001)-oriented device,the(111)-oriented FTJ shows a sharper and faster switching between the ON and OFF states according to the nucleation-limited-switching dynamics model,giving rise to good linearity in memristive behaviors for synaptic plasticity and reliable retention and endurance properties for the resistance switching.The improved TER properties are ascribed to larger effective polarizations and 180°switching in the(111)-oriented PZT barrier.These results facilitate the design and fabrication of high-performance FTJ devices with the optimization of crystallographic orientation and polarization switching characteristics.展开更多
Magnetic vortices hold great promise for advanced information storage applications due to their quartet degenerate states and high topological stability.The key to their application lies on meticulous control of its p...Magnetic vortices hold great promise for advanced information storage applications due to their quartet degenerate states and high topological stability.The key to their application lies on meticulous control of its polarity and chirality,which traditionally relies on magnetic fields,currents,and spin waves.However,the vortex core’s intrinsic precession under these stimuli hampers fast switching of the polarity and chirality.Here,we demonstrate a fast and precise control of polarity and chirality in magnetic vortices using combined femtosecond(fs)laser and tiny magnetic fields via micromagnetic simulations on Permalloy nanodisks.The fs laser pulse induces an ultrafast quench effect to establish the initial paramagnetic state,while the simultaneously applied magnetic fields precisely target the final vortex structure.Intriguingly,a 110 mT out-ofplane field and a 7 mT in-plane circular field are sufficient to realize precise control of the polarity and chirality on sub-nanosecond time scale,respectively,which are much lower than that of the previous work.Our approach guarantees fast and reliable switching of magnetic vortex polarity and chirality,paving the groundwork for a high-speed quaternary data storage and contributing a novel perspective to the fundamentals of spintronics.展开更多
The semiconductor optical amplifier （SOA） has obvious advantages in all-optical signal processing, because of the simple structure, strong non-linearity, and easy integration. A variety of all-optical signal process...The semiconductor optical amplifier （SOA） has obvious advantages in all-optical signal processing, because of the simple structure, strong non-linearity, and easy integration. A variety of all-optical signal processing functions, such as all-optical wavelength conversion, all-optical logic gates and all-optical sampling, can be completed by SOA. So the SOA has been widespread concerned in the field of all-optical signal processing. Recently, the polarization rotation effect of SOA is receiving considerable interest, and many researchers have launched numerous research work utilizing this effect. In this paper, a new all-optical flip-flop structure using polarization switch （PSW） based on polarization rotation effect of SOA is presented.展开更多
Typically,conducting polymers transfer either electrons or holes.It is rare to see high bipolar(p-and n-type)electrical conductivities within a single bulk doped organic polymer without the assistant of gate voltage.H...Typically,conducting polymers transfer either electrons or holes.It is rare to see high bipolar(p-and n-type)electrical conductivities within a single bulk doped organic polymer without the assistant of gate voltage.Herein,we report that FeCl3-doped solutionprocessable D–A copolymer poly(2,5-bis(2-octyldo decyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophen)(DPPTTT)could exhibit a high p-type electrical conductivity of 130.6 S/cm and a good n-type electrical conductivity of 14.2 S/cm by engineering the doping level.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61178011,61275116,and 61475127)the Natural Science Foundation of Chongqing City,China(Grant No.2012jjB40011)
文摘The polarization switching（PS） and polarization bistability（PB） characteristics of a 1550-nm vertical-cavity surfaceemitting laser（VCSEL） subjected to orthogonal optical injection are systematically investigated.The simulated results show that the PS and polarization-resolved nonlinear dynamical states of the VCSEL are critically dependent on the changing paths of the injected power.The polarization dynamics for different scanning directions of the injected power is presented to explain the polarization evolution during the formation of PS.In the case of forward scanning injected power,with the increase of frequency detuning level between the VCSEL and the injected light,the injected power required for PS gradually increases for negative frequency detuning but exhibits fluctuations for positive frequency detuning.In the case of reversely scanning injected power,the injected power required for PS displays fluctuant changes within the whole frequency detuning range.Specifically,PS may disappear under certain negative frequency detuning and large bias current.Furthermore,the hysteresis width as a function of the frequency detuning is calculated,and the regions for the appearance and disappearance of PB have been determined in the parameter space of the bias current and frequency detuning.
文摘Broad-band all-optical wavelength conversion of differential phase-shift keyed （DPSK） signal is experimentally demonstrated. This scheme is composed of a one-bit delay interferometer demodulation stage followed by a semiconductor optical amplifier （SOA） based nonlinear polarization switch. A wavelength converter for the 10 G b/s DPSK signal is presented, which has a wide wavelength range of more than 30 nm. The converted signals experience small power penalties less than 1.4 dB compared with the original signal, at a bit error rate of 10-9. Additionally, the optical spectra, the measured waveforms and the open eye diagrams of the converted signals show a high quality wavelength conversion performance.
基金supported by the National Natural Science Foundation of China (Grant No. 30870662)
文摘This paper demonstrates the influence of external optical feedback on the polarization state of longitudinal modes in quasi-isotropic microchip Nd：YAG lasers. Under optical feedback, the polarization state of longitudinal modes in quasi-isotropic lasers relies strongly on the intracavity anisotropy loss and mode competition. When the intracavity anisotropy loss is small, external optical feedback can cause polarization switching and strong mode competition between two orthogonal linearly polarized eigenstates of one laser longitudinal mode, which leads to the distortion of laser intensity modulation waveform. The polarization switching is independent of the initial external cavity length. By increasing the intracavity anisotropy loss, one polarization eigenstate can be suppressed and the laser works in single-polarization state. A theoretical analysis based on the compound cavity model is presented, which is in good agreement with the experimental results. The results offer guidance to the development of laser feedback interferometers.
基金supported by the National Key Research and Development Program of China “National Quality Infrastructure” (Grant No. 2021YFF0600902)。
文摘The research of high-performance polarization controllers is of great significance for expanding the application field of polarization optics. Here, a polarization switch is demonstrated by using a dual-core photonic crystal fiber(DCPCF)with four symmetrical air holes, placed above and below each core, filled with magnetic fluid(MF). The switch, which utilizes a magnetic field to change the coupling length ratio of the x and y polarization modes, enables dynamic tuning of the polarization state and extinction ratio. Numerical results show that when the working length is 36.638 mm, the magneto–optical polarization switch can operate in four communication bands, i.e., 1509 nm to 1520 nm, 1544 nm to1556 nm, 1578 nm to 1591 nm, and 1611 nm to 1624 nm. Moreover, the extinction ratio(ER) is greater than 20 d B in the fiber length range of 38.5 mm to 38.7 mm, indicating that the device has a good fault tolerance for the interception of the fiber length.
基金supported by the National Natural Science Foundation of China(Grant Nos.51075335,51174168,10902086,and 50875217)the NPU Foundation for Fundamental Research(Grant No.JC201005)
文摘The ferroelectric domain formation(FDF) and polarization switching(FDPS) subjected to an external electric field are simulated using the phase-field(PF) method,and the FDPS mechanism under different external electric fields is discussed.The results show that the FDF is a process of nucleation and growth in ferroelectric without applying any external stress.Four kinds of parallelogram shaped ferroelectric domains are formed at the steady state,in which the 180° anti-phase domains regularly align along the 45° direction and the 90° anti-phase domains regularly distribute like a stepladder.Steady electric fields can rotate domain polarization by 90° and 180°,and force the orientation-favorite domains and the average polarization to grow into larger ones.The greater the steady electric field,the larger the average polarization at the steady state.In ferroelectrics subject to an alternating electric field,domain polarization switches to cause a hysteresis loop and an associated butterfly loop with the alternating electric field.The coercive field and remnant field are enhanced with the increase of the electric field frequency or strength,or with the decrease of temperature.
基金supported by the National Basic Research Program of China(Grant No.2013CB934003)the State Key Laboratory of Software Development Environment(Grant No.SKLSDE-2013ZX-28)
文摘Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device.The dependencies of electron spin-polarization on the strip’s magnetization strength,width and position have been systematically investigated.A novel magnetic control spin-polarization switch is proposed by inserting a ferromagnetic metal(FM)strip eccentric in relation to off the center of the spin filter,which produces the first energy level spin-polarization reversal.It is believed to be of significant importance for the realization of semiconductor spintronics multiple-value logic devices.
基金supported by the National Natural Science Foundation of China(Nos.60977008and60678048)the National Ministry Education Fund for Doctoral of China(No.20103219110014)the Chinese Academy of Sciences Key Laboratory Fund(No.2008DP173445)
文摘This letter shows that the human eye fundus tissue has higher reflectivity at the near-infrared （NIR） wavelength, and that some aberrations exist at the pre-optical system from cornea to vitreous. We design a NIR fundus camera with inner focusing, which can be applied to the -10 D to 10 D range of vision and has the advantage of ensuring the stability of image when is focused. Considered as Liou＇s eye aberration model, we correct the integrated aberration to ensure a 100 lp/mm resolution when we complete the assembly and calibration of the fundus camera. Kohler illumination is also applied to obtain uniform fundus illumination. Moreover, we put forward a novel method for stray light elimination based on polarization switch, which inhibits ghost image formation near the focal plane when the illumination beam is reflected by the eyepiece surface. The result shows that this method is effective in ensuring an illumination uniformity of 80%, with the advantage of simple structure and easy assembly.
基金the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20070613058)the Foundation for Key Program of the Ministry of Education, China (Grant No. 105148)and the Doctoral Innovation Fund of Southwest Jiaotong University
文摘We perform a theoretical study on the polarization-resolved compound lasing mode （CLM） of two mutually coupled vertical-cavity surface-emitting lasers （VCSELs）. Different solutions of CLMs are derived though stability analysis of the spin-flip model. The dynamical evolvements of CLMs with the existence of polarization degrees of freedom are also charactered. The most stable CLM with the smallest carrier density tend to be excited, since the gain needed for this mode to emit is the lowest. In the given system, varying values of injection rate or birefringence, etc., will change the generation of the preferred CLMs in the two polarization directions, and thus influence the polarization switching （PS） characteristics. Thus, hoppings between CLMs are also companied by PSs. Through mapping of average power in the parameter space, the influences of coupling rate and anisotropy parameters （linear dichroism and linear birefringence） on PS and hopping between CLMs are discussed.
基金supported by the China Postdoctoral Science Foundation(Grant No.2013M541286)the Science and Technology Planning Project of Jilin Province,China(Grant Nos.20140520109JH and 20150414003GH)the “Twelfth Five year” Scientific and Technological Research Project of Department of Education of Jilin Province,China
文摘We perform micromagnetic simulations on the switching of magnetic vortex core by using spin-polarized currents through a three-nanocontact geometry. Our simulation results show that the current combination with an appropriate current flow direction destroys the symmetry of the total effective energy of the system so that the vortex core can be easier to excite,resulting in less critical current density and a faster switching process. Besides its fundamental significance, our findings provide an additional route to incorporating magnetic vortex phenomena into data storage devices.
基金supported by the National Natural Science Foundation of China (2371235,92061107,92161203)。
文摘Achieving simultaneous polarization and spin switching at room temperature is essential for advanced multi-state storage and control applications,particularly in magnetoelectrics and electron spintronics,yet such materials are exceedingly rare.Based on polar molecular valence tautomerism of Co^(Ⅲ)(3,5-DBcat)(3,5-DBsq)(trans-4-stypy)_(2)(1),room-temperature spin and polarization switching was achieved via electron transfer.Notably,the ferroelectric polarization and spin switching in 1 are modulated by both temperature and light.The successful implementation of room-temperature polarization and spin switching in 1 signifies an important advancement toward practical applications.
基金Project supported by the National Natural Science Foundation of China(Grant No.61475120)the Innovative Projects in Guangdong Colleges and Universities,China(Grant No.2015KTSCX146)
文摘In a chaotic system of vertical cavity surface emitting laser （VCSEL） with external optical-injection, we propose a novel implementation scheme for reconfigurable dynamic all-optical chaotic logic operations （AOCLOs）. Under different key parameters, such as the bias current, the injection strength and the frequency detuning of the injected light field and the VCSEL, we also explore the evolutions of the polarization-bistability with the amplitude of the injected light field when the output of VCSEL is chaotic wave. According to the dynamic evolutions, we find out the optimal value of the frequency detuning that is considered as a control logic signal, and further implement different AOCLOs, such as AND, NAND, OR, NOR, XOR, and XNOR, by controlling the logic operation of the control logic signal between two logic inputs. Moreover, the ability to reconstruct these logic operations is demonstrated under relatively low noise strength of the spontaneous emission.
文摘Nonlinear electro-mechanical behaviors of piezoelectric materials and viscoelastic nature of polymers result in the overall nonlinear and hysteretic responses of active polymeric composites. This study presents a hybrid-unit-cell model for obtaining the effective nonlinear and rate-dependent hysteretic electro-mechanical responses of hybrid piezocomposites. The studied hybrid piezocomposites consist of unidirectional piezoelectric fibers embedded in a polymeric matrix, which is reinforced with piezoelectric particles. The hybrid-unit-cell model is derived based on a unit-cell model of fiber-reinforced composites consisting of fiber and matrix subcells, in which the matrix subcells are comprised of a unit-cell model of particle-reinforced composites. Nonlinear electro-mechanical responses are considered for the piezoelectric constituents while a viscoelastic solid constitutive model is used for the polymer constituent. The hybrid-unit cell model is used to examine the effects of different responses of the constituents, microstructural arrangements, and loading histories on the overall nonlinear and hysteretic electro-mechanical responses of the hybrid piezocomposites, which are useful in designing active polymeric composites.
基金the National Natural Science Foundation of China(52302217,52102150)the Natural ScienceFoundation in Hunan Province of China(2024JJ6028)+1 种基金The Science and Technology Innovation Program of Hunan Province(2022RC1029)Central South University Research Programme of Advanced Interdisciplinary Studies(2023QYJC036).
文摘HfO_(2)-based ferroelectricfilms have been extensively explored and utilized in thefield of non-volatile memory and electrical programmability.However,the trade-off between ferroelectric polarization and dielectric constant in HfO_(2)has limited the overall performance improvement of devices in practical applications.Herein,a novel approach is proposed for the Hf_(0.5)Zr_(0.5)O_(2)/ZrO_(2)(HZO/ZrO_(2))nanobilayer engineering,which can effectively regulate the phase structure evolution of HfO_(2)films to construct a suitable morphotropic phase boundary(MPB).Thefindings highlight that the top ZrO_(2)layer can regularly promote the formation of either the ferroelectric o-phase or the antiferroelectric t-phase.An ideal MPB is successfully established in HZO/ZrO_(2)(6/9 nm)nanobilayerfilm by carefully optimizing the HZO/ZrO_(2)thickness ratio,which presents a high dielectric constant of 52.7 and a large 2Pr value of up to 72.3 mC/cm^(2)without any wake-up operation.Moreover,the HZO/ZrO2 nanobilayer thinfilms demonstrate faster polarization switching speed(1.09μs)and better fatigue performance(10^(9)cycles)compared to the conventional HZO solid solutionfilms.The relationship between ferroelectric and dielectric properties can be harmoniously balanced through the designation.The results indicate that the HZO/ZrO_(2)nanobilayer engineering strategy is quite potential to pave the way for the development of nextgeneration memory technologies with superior performance and reliability.
基金supported by JSPS KAKENHI(grant nos.23H04862,24K21783,24K17698 and 23K04681)support from the Murata Science and Education Foundation(grant no.M24AN117)The synchrotron radiation experiments were performed at the BL01B1 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute(proposal no.2021B1342)。
文摘Macroscopic polarization switching achieved through directional electron transfer or spin crossover(SCO)has attracted considerable attention because of its potential applications in data storage devices,sensors,and energy converters.Here,by substituting the central metal and anion of a reported compound,[Fe(RR-cth)Co(SS-cth)(μ-dhbq)](AsF_(6))_(3),we obtained two dinuclear compounds that crystallize in the polar space group,P2_(1),[Fe(RR-cth)Ga(SS-cth)(μ-dhbq)](X)_(3)(X=AsF_(6)and ClO_(4)).Among them,complex 1(AsF_(6))_(3)exhibited a two-step magnetic transition,including SCO behavior near 50 K and a gradual valence tautomerism(VT)behavior that occurred over a wide temperature range up to at least 250 K.The SCO behavior of complex 1(AsF_(6))_(3)can be triggered by changes in temperature or the application of magnetic fields,leading to a polarization change of approximately 0.5μC cm^(−2).The transition entropy of 55.9 J K^(−1)mol^(−1)during the SCO process was obtained using the Clausius-Clapeyron equation.Contrarily,complex 1(ClO_(4))_(3)only exhibited gradual VT behavior from a low temperature to room temperature.Single-crystal X-ray diffraction,variable-temperature infrared spectroscopy,and pyroelectric measurements confirmed the gradual VT process that occurs over a wide temperature range in both complexes.This study broadens the range of polarization switching molecular systems by replacing the central metal and anion,thereby facilitating the development of multifunctional molecular materials.
文摘Titration of pesticides onto sorption sites can determine sorption capacities on soils. Previous studies have tracked the sorption capacities and detailed kinetics of the uptake of atrazine and its decomposition byproduct hydroxyatrazine on different soils, including measurements made using LC-MS/MS. These studies have now been extended to explore sorption-desorption equilibria for a mixture of pesticides from soil using LC-MS/MS. Desorption of sorbed pesticide residues has environmental regulatory implications for pesticide levels in runoff, or for longer term sequestration, partitioning, and transport. The uptake of pesticides by the soil at equilibrium was measured for a number of different concentrations, and sorption capacities were estimated. Pesticide-soil interaction studies were conducted by exposing standard stock solutions of pesticide mixtures to a characterized Nova Scotia soil. The mixture contained atrazine and dicamba. Initial aqueous mixture concentrations ranging from 5 × 10<sup>-9</sup> to 10<sup>-5</sup> M or greater were exposed to 25 mg aliquots of soil and allowed to reach equilibrium. The total uptake of each pesticide was measured indirectly, by measuring the concentration remaining in solution using an IONICS 3Q 120 triple quadrupole mass spectrometer. These sorption capacities have been supplemented by studies examining equilibrium recovery rates from soil aliquots with different initial uptakes. This gives insight into the fraction of easily recoverable (reversibly sorbed) pesticides on the soil. Proper quantification of equilibrium constants and kinetic rate coefficients using high performance LC-MS/MS facilitates the construction of accurate, predictive models. Predictive kinetic models can successfully mimic the experimental results for solution concentration, labile sorption, and intra-particle diffusion, and could be used to guide regulatory practices.
基金supported by the Key R&D Program of Zhejiang Province(No.2019C03065)。
文摘Silicon waveguides typically exhibit optical anisotropy,which leads to polarization correlation and single-polarization operations.This consequently creates a demand for polarization-control devices.This paper introduces a CMOS-compatible O-band reconfigurable TE/TM polarization rotator comprising two symmetrical polarization rotator-splitters and phase shifters.This configuration enables dynamic conversion of any linear polarization to its quadratic equivalent.Experimental results indicate that the reconfigurable polarization rotator exhibits an insertion loss of less than 1.5 dB.Furthermore,the bandwidth for a polarization extinction ratio beyond 15 dB exceeds 60 nm.
基金sponsored by the National Natural Science Foundation of China(No.52372113).
文摘Orientation anisotropy is a well-known essential character for polarization characteristics of ferroelectric materials,which has been widely investigated in conventional ferroelectric random access memories.In this work,we study the effects of orientation on the tunneling electroresistance(TER)of ferroelectric tunnel junctions(FTJs).Rhombohedral Pb(Zr_(0.7),Ti_(0.3))O_(3)(PZT)that has the polar axis along the(111)orientation is adopted as potential barriers and two kinds of FTJs that are composed of(001)-and(II1)-oriented PZT barriers and Nb:SrTiO_(3)(Nb:STO)electrodes,respectively,are fabricated.The(111)-oriented P1PZT/Nb:STO FTJ exhibits a giant ON/OFFratio of~1.9×10^(5),about 30 times that of the(001)-oriented device,due to the lowered PZT barrier in the ON state and the widen Schottky barrier in the OFF state based on current and capacitance analyses.In addition,compared to the(001)-oriented device,the(111)-oriented FTJ shows a sharper and faster switching between the ON and OFF states according to the nucleation-limited-switching dynamics model,giving rise to good linearity in memristive behaviors for synaptic plasticity and reliable retention and endurance properties for the resistance switching.The improved TER properties are ascribed to larger effective polarizations and 180°switching in the(111)-oriented PZT barrier.These results facilitate the design and fabrication of high-performance FTJ devices with the optimization of crystallographic orientation and polarization switching characteristics.
基金supported by the National Key Research and Development Program of China(Grant No.2020YFA0309300)the National Natural Science Foundation of China(NSFC)(Grant Nos.12127803 and 12304146)+5 种基金China Postdoctoral Science Foundation(No.2023M741828)Science and Technology Projects in Guangzhou(Grant No.202201000008)Guangdong Basic and Applied Basic Research Foundation(Grant Nos.2021B1515120047 and 2023B1515020112)the Natural Science Foundation of Tianjin(Grant No.20JCJQJC00210)the 111 Project(Grant No.B23045)the“Fundamental Research Funds for the Central Universities”,Nankai University(Grant Nos.63213040,C029211101,C02922101,ZB22000104,DK2300010207,63243194,and 9242000728).
文摘Magnetic vortices hold great promise for advanced information storage applications due to their quartet degenerate states and high topological stability.The key to their application lies on meticulous control of its polarity and chirality,which traditionally relies on magnetic fields,currents,and spin waves.However,the vortex core’s intrinsic precession under these stimuli hampers fast switching of the polarity and chirality.Here,we demonstrate a fast and precise control of polarity and chirality in magnetic vortices using combined femtosecond(fs)laser and tiny magnetic fields via micromagnetic simulations on Permalloy nanodisks.The fs laser pulse induces an ultrafast quench effect to establish the initial paramagnetic state,while the simultaneously applied magnetic fields precisely target the final vortex structure.Intriguingly,a 110 mT out-ofplane field and a 7 mT in-plane circular field are sufficient to realize precise control of the polarity and chirality on sub-nanosecond time scale,respectively,which are much lower than that of the previous work.Our approach guarantees fast and reliable switching of magnetic vortex polarity and chirality,paving the groundwork for a high-speed quaternary data storage and contributing a novel perspective to the fundamentals of spintronics.
基金Thanks to the financial supports from the National Natural Science Foundations of China （61378061 and 61575026）.
文摘The semiconductor optical amplifier （SOA） has obvious advantages in all-optical signal processing, because of the simple structure, strong non-linearity, and easy integration. A variety of all-optical signal processing functions, such as all-optical wavelength conversion, all-optical logic gates and all-optical sampling, can be completed by SOA. So the SOA has been widespread concerned in the field of all-optical signal processing. Recently, the polarization rotation effect of SOA is receiving considerable interest, and many researchers have launched numerous research work utilizing this effect. In this paper, a new all-optical flip-flop structure using polarization switch （PSW） based on polarization rotation effect of SOA is presented.
基金support from the National Natural Science Foundation of China(grant no.51876151)the Fundamental Research Funds for the Central Universities,the World-Class Universities(Disciplines)+1 种基金the Characteristic Development Guidance Funds for the Central Universities(grant no.PY3A010)and the start-up funding from Xi’an Jiaotong University(grant no.QY1J003)the HPC platform and the Instrument Analysis Center,Xi’an Jiaotong University.
文摘Typically,conducting polymers transfer either electrons or holes.It is rare to see high bipolar(p-and n-type)electrical conductivities within a single bulk doped organic polymer without the assistant of gate voltage.Herein,we report that FeCl3-doped solutionprocessable D–A copolymer poly(2,5-bis(2-octyldo decyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophen)(DPPTTT)could exhibit a high p-type electrical conductivity of 130.6 S/cm and a good n-type electrical conductivity of 14.2 S/cm by engineering the doping level.
