SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure ...SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure of SrBi4Ti4015 （SBTi）. The coercive filed （Ec） and remnant polarisation （Pr） increase at first, then decrease with the increase of Fe doping content. At a maximum applied field of 229 kV/cm, the 2Pr reaches a maximum value of 91.1μC/cm2 at x = 0.05 and the corresponding Ec is 72 kV/cm. The 2Pr increases by about 260% and the Ec decreases by about 6%, respectively. Obviously, the ferroelectric property of SrBi4Ti4015 is greatly enhanced by Fe doping. The fatigueendurance characteristic of the SBFT-0.05 is not improved. After 1.1× 10^9 read/write cycles at a frequency of 50 kHz, the nonvolatile polarisations （Pnv = P＊ - P^） decreased about 48% of its initial value.展开更多
A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a ...A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.展开更多
We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is real...We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.展开更多
This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatc...This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.展开更多
We numerically calculate and analyse the electromagnetic fields, optical intensity distributions, polarization states and orbital angular momentum of some elliptic hollow modes in an elliptic dielectric hollow fiber ...We numerically calculate and analyse the electromagnetic fields, optical intensity distributions, polarization states and orbital angular momentum of some elliptic hollow modes in an elliptic dielectric hollow fiber （EDHF） by using Mathieu functions, and also calculate the optical potential of the blue-detuned eHE11 mode evanescent-light wave for ^85Rb atoms, including the position-dependent van der Waals potential, and discuss briefly some potential applications of our EDHF in atom and molecule optics, etc. Our study shows that the vector electric field distributions of the odd modes in the cross section of the EDHF are the same as that of the even modes and with different boundary ellipses by rotating an angle of π/2, and the orbital angular momentum （OAM） of single HE （EH） mode is exactly equal to zero, while that of dual-mode in the EDHF is fractional in h, and has a sinusoidal oscillation as z varies. The EDHF can be used to produce various elliptic hollow beams, even to generate and study various atomic vortices with a fractional charge and its fractional quantum Hall effect in atomic Bose Einstein condensate, and so on.展开更多
Charging is one of the most important reliability issues in radio frequency microelectro- mechanical systems （RF MEMS） capacitive switches since it makes the actuation voltage unstable. This paper proposes a hybrid ...Charging is one of the most important reliability issues in radio frequency microelectro- mechanical systems （RF MEMS） capacitive switches since it makes the actuation voltage unstable. This paper proposes a hybrid model to describe the transient dielectric charging and discharging process in the defect-rich amorphous SiO2 RF MEMS capacitive switches and verifies experimentally. The hybrid model contains two parts according to two different charging mechanisms of the amorphous SiO2, which are the polarisation and charge injection. The models for polarisation and for charge injection are established, respectively. Analysis and experimental results show that polarisation is always effective, while the charge injection has a threshold electric field to the amorphous SiO2 film. Under different control voltage conditions, the hybrid model can accurately describe the experimental data.展开更多
We study the relationship between electromagnetically-induced transparency（EIT） and Autler–Townes（AT） splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the flu...We study the relationship between electromagnetically-induced transparency（EIT） and Autler–Townes（AT） splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.展开更多
The filter made up of two gratings performs as a two-dimensional non-spatial filtering. This paper reports that the volume Bragg gratings are fabricated by interfering two collimated coherent laser beams in photopolym...The filter made up of two gratings performs as a two-dimensional non-spatial filtering. This paper reports that the volume Bragg gratings are fabricated by interfering two collimated coherent laser beams in photopolymer. Diffraction efficiency of a single grating is up to 78% in Bragg＇s condition, then a two-dimensional non-spatial filter, which consists of two volume Bragg gratings and a half-wave plate, enables the laser beam filtered in two dimensions with the diffraction efficiency of 54%. The Bragg＇s condition and effect of polarisation on performances of the two-dimension filter are also discussed.展开更多
The modified dipolar Poisson-Boltzmann （MDPB） equation, where the electrostatics of the dipolar interactions of solvent molecules and also the finite size effects of ions and dipolar solvent molecules are explicitly...The modified dipolar Poisson-Boltzmann （MDPB） equation, where the electrostatics of the dipolar interactions of solvent molecules and also the finite size effects of ions and dipolar solvent molecules are explicitly taken into account on a mean-field level, is studied numerically for a two-plate system with oppositely charged surfaces. The MDPB equation is solved numerically, using the nonlinear Multigrid method, for one-dimensional finite volume meshes. For a high enough surface charge density, numerical results of the MDPB equation reveal that the effective dielectric constant decreases with the increase of the surface charge density. Furthermore, increasing the salt concentration leads to the decrease of the effective dielectric constant close to the charged surfaces. This decrease of the effective dielectric constant with the surface charge density is opposite to the trend from the dipolar Poisson Boltzmann （DPB） equation. This seemingly inconsistent result is due to the fact that the mean-field approach breaks down in such highly charged systems where the counterions and dipoles are strongly attracted to the charged surfaces and form a quasi two-dimensional layer. In the weak-coupling regime with the electrostatic coupling parameter （the ratio of Bjerrum length to Gouy-Chapman length） Ξ 〈 1, where the MDPB equation works, the effective dielectric constant is independent of the distance from the charged surfaces and there is no accumulation of dipoles near the charged surfaces. Therefore, there are no physical and computational advantages for the MDPB equation over the modified Poisson-Boltzmann （MPB） equation where the effect of dipolar interactions of solvent dipoles is implicitly taken into account in the renormalised dielectric constant.展开更多
Polycrystalline ferroelectric Bi3.25La0.75Ti3O12 thin films are prepared on Pt/Ti/SiO2/Si substrates by the conventional metalorganic decomposition method. It is observed that with the increase of switching pulse widt...Polycrystalline ferroelectric Bi3.25La0.75Ti3O12 thin films are prepared on Pt/Ti/SiO2/Si substrates by the conventional metalorganic decomposition method. It is observed that with the increase of switching pulse width, the remnant polarisation and the coercive field increase. A wider switching pulse can result in poorer fatigue properties, which comes from more charged defects diffusing to and being trapped on domain walls. On the other hand, when the compressive stress is applied to films, the fatigue properties can be improved. This phenomenon is due to the reorientation of domains under stress.展开更多
We study the electromagnetically-induced transparency（EIT） in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and...We study the electromagnetically-induced transparency（EIT） in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and the EIT resonance reflects mainly the characteristics of the nonlinear susceptibility. It is found that the macroscopic polarization interference effect plays a crucial role in determining the EIT resonance spectrum. To obtain a Doppler-free spectrum there must be polarization interference between atoms of different velocities. A dressed-state model, which analyzes the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting, is employed to explain the results.展开更多
We study phase-conjugate six-wave mixing spectroscopy based on electromagnetically-induced-transparency in a Doppler-broadened folded four-level system. It is found that the six-wave mixing spectrum can be either Dopp...We study phase-conjugate six-wave mixing spectroscopy based on electromagnetically-induced-transparency in a Doppler-broadened folded four-level system. It is found that the six-wave mixing spectrum can be either Doppler-free or very broad, depending on whether the interference between the polarisations of atoms with different velocities is constructive or destructive. To obtain the Doppler-free six-wave mixing spectrum in the folded four-level system, the conditions are more stringent in comparison with those in the cascade and N-type four-level systems. This polarisation interference can be controlled in the presence of a strong coupling field.展开更多
A dual optical tweezers system, which consists of a doughnut mode optical tweezer （DMOT） with the azimuthally polarised trapping beam and a solid mode optical tweezer （SMOT） with the Gauss trapping beam was constr...A dual optical tweezers system, which consists of a doughnut mode optical tweezer （DMOT） with the azimuthally polarised trapping beam and a solid mode optical tweezer （SMOT） with the Gauss trapping beam was constructed to compare the axial trapping effect of DMOT and SMOT. The long-distance axial trapping of ST68 microbubbles （MBs） achieved by DMOT was more stable than that of SMOT. Moreover the axial trapping force measured using the viscous drag method, was depended on the diameter of the particle, the laser power, and the numerical aperture （NA） of the objective lens. The measurement of the axial trapping force and the acquisition of CCD images of trapping effect confirmed that the DMOT showed excellent axial trapping ability than SMOT. A simple and effective method is developed to improve axial trapping effect using the azimuthally polarized beam as trapping beam. This is helpful for the long-distance manipulating of particles especially polarised biological objects in axial direction.展开更多
We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al. in 1987 （Tian B, Wu G, Liu G 1987 J. Chem. Phys. 87 7300）. The bond polarisab...We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al. in 1987 （Tian B, Wu G, Liu G 1987 J. Chem. Phys. 87 7300）. The bond polarisabilities provide much information concerning the electronic structure of the non-resonant Raman excited virtual state. At the initial moment by the 514.5 nm excitation, the tendency of the excited electrons （mapped out by the bond polarisabilities） is to spread to the molecular periphery, and the electronic structure of the Raman virtual state is close to the pseudoquinonoidic state. When the final stage of relaxation is approached, the bond polarisabilities of those peripheral bonds relax faster than those closer to the molecular core, the phenyl ring. The molecule is in the benzenoidic form as demonstrated by the bond polarisabilities after relaxation.展开更多
We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum informati...We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum information processing. The scheme employs a photon with linearly polarisation interacting one after the other with two remote quantum-dot spins in cavities. Due to the optical spin selection rule, the photon obtains a Faraday rotation after the interaction process. By measuring the polarisation of the final output photon, a non-local two-qubit phase gate between the two remote quantum-dot spins is constituted. Our scheme may has very important applications in the distributed quantum information processing.展开更多
作为技术领先型的民族企业,算通科技日前在CCBN2016的展台上,从三大部分展示了自己的技术实力。一是保障了传统广电运营又保护了融合媒体O T T内容安全的＂CA S＋DR M解决方案＂;二是适应三网融合、有线无线卫星融合一体化的前端硬件产...作为技术领先型的民族企业,算通科技日前在CCBN2016的展台上,从三大部分展示了自己的技术实力。一是保障了传统广电运营又保护了融合媒体O T T内容安全的＂CA S＋DR M解决方案＂;二是适应三网融合、有线无线卫星融合一体化的前端硬件产品;三是进一步优化整合的算通＂增值＋＂业务体系。三个产品线都是算通的支柱产品,每个展区都有自己的亮点,比如高安芯片DRM、AVS＋编转码系统、Polaris V综合增值平台等。展开更多
文摘SrBi4-xFexTi4015 （SBFT-x） thin films （x = 0.00, 0.05, 0.08, 0.15） have been synthesized on Pt/Ti/SiO2/Si （100） substrates by sol-gel method. This paper finds that Fe-doping does not change the crystal structure of SrBi4Ti4015 （SBTi）. The coercive filed （Ec） and remnant polarisation （Pr） increase at first, then decrease with the increase of Fe doping content. At a maximum applied field of 229 kV/cm, the 2Pr reaches a maximum value of 91.1μC/cm2 at x = 0.05 and the corresponding Ec is 72 kV/cm. The 2Pr increases by about 260% and the Ec decreases by about 6%, respectively. Obviously, the ferroelectric property of SrBi4Ti4015 is greatly enhanced by Fe doping. The fatigueendurance characteristic of the SBFT-0.05 is not improved. After 1.1× 10^9 read/write cycles at a frequency of 50 kHz, the nonvolatile polarisations （Pnv = P＊ - P^） decreased about 48% of its initial value.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60877037 and 10564005)
文摘A novel Whispering-Gallery-Mode （WGM） fibre laser, emitting linearly polarised three-colour light, is demonstrated by pumping and gain coupling with evanescent waves. The pump light is longitudinally coupled into a bare optical fibre immersed in a dye solution of lower refractive index. The dye molecules around the bare fibre are excited by the evanescent waves of pump light when they propagate along the fibre in a total internal reflection. When the pump beam within the fibre is a meridian beam, the WGM lasing emission from the fibre laser is a linearly polarised transverse electric wave, while it is a mixed wave of the linearly polarised transverse electric and magnetic waves if the pump beam is a skew beam within the fibre. Because the excited molecules are located within the evanescent field of WGM, a good spatial overlap between the dye gain and the evanescent field leads to a high pumping efficiency and a longer gain distance along the fibre. Once the bare fibre is inserted into three glass capillaries filled with Rhodamine 6G, 610 and 640 dye solutions, respectively, WGM laser oscillations at the wavelengths of 567-575, 605-614 and 656-666 nm occur simultaneously, and a linearly polarised three-colour lasing emission is achieved in a single optical fibre.
文摘We report the femtosecond(fs)laser fabrication of biomimetic omnidirectional iridescent metallic surfaces exhibiting efficient diffraction for practically any angle of light incidence.Such diffractive behavior is realized by means of multi-directional low-spatial-frequency,laser-induced periodic surface structures(LSFL)formed upon exploiting the cylindrical symmetry of a cylindrical vector(CV)fs field.We particularly demonstrate that the multi-directional gratings formed on stainless steel surface by a radially polarized fs beam,could mimic the omnidirectional structural coloration properties found in some natural species.Accordingly,the fabricated grating structures can spatially disperse the incident light into individual wavelength with high efficiency,exhibiting structural iridescence at all viewing angles.Analytical calculations using the grating equation reproduced the characteristic variation of the vivid colors observed as a function of incident angle.We envisage that our results will significantly contribute to the development of new photonic and light sensing devices.
基金supported from the Major Program of Science Foundation of Xi’an University of Arts and Science
文摘This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10374029,10434060 and 10674047)the National Key Basic Research and Development Program of China(Grant No.2006CB921604)+1 种基金the Basic Key Program of Shanghai Municipality(Grant No.07JC14017)the Program for Changjiang Scholar and Innovative Research Team,and Shanghai Leading Academic Discipline Project(Grant No.B408)
文摘We numerically calculate and analyse the electromagnetic fields, optical intensity distributions, polarization states and orbital angular momentum of some elliptic hollow modes in an elliptic dielectric hollow fiber （EDHF） by using Mathieu functions, and also calculate the optical potential of the blue-detuned eHE11 mode evanescent-light wave for ^85Rb atoms, including the position-dependent van der Waals potential, and discuss briefly some potential applications of our EDHF in atom and molecule optics, etc. Our study shows that the vector electric field distributions of the odd modes in the cross section of the EDHF are the same as that of the even modes and with different boundary ellipses by rotating an angle of π/2, and the orbital angular momentum （OAM） of single HE （EH） mode is exactly equal to zero, while that of dual-mode in the EDHF is fractional in h, and has a sinusoidal oscillation as z varies. The EDHF can be used to produce various elliptic hollow beams, even to generate and study various atomic vortices with a fractional charge and its fractional quantum Hall effect in atomic Bose Einstein condensate, and so on.
基金supported by the National Natural Science Foundation of China (Grant No. 60676043)
文摘Charging is one of the most important reliability issues in radio frequency microelectro- mechanical systems （RF MEMS） capacitive switches since it makes the actuation voltage unstable. This paper proposes a hybrid model to describe the transient dielectric charging and discharging process in the defect-rich amorphous SiO2 RF MEMS capacitive switches and verifies experimentally. The hybrid model contains two parts according to two different charging mechanisms of the amorphous SiO2, which are the polarisation and charge injection. The models for polarisation and for charge injection are established, respectively. Analysis and experimental results show that polarisation is always effective, while the charge injection has a threshold electric field to the amorphous SiO2 film. Under different control voltage conditions, the hybrid model can accurately describe the experimental data.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11404330,11274376,61308011,and 11474347)the NSAF,China(Grant No.U1330117)+1 种基金the National Basic Research Program of China(Grant Nos.2013CB922002 and 2010CB922904)the China Postdoctoral Science Foundation(Grant No.119103S239)
文摘We study the relationship between electromagnetically-induced transparency（EIT） and Autler–Townes（AT） splitting in a cascade three-level Doppler-broadened system. By comparing the absorption spectrum with the fluorescence excitation spectrum, it is found that for a Doppler-broadened system, EIT resonance cannot be explained as the result of quantum interference, unlike the case of a homogeneously broadened system. Instead, the macroscopic polarization interference plays an important role in determining the spectra of EIT and AT splitting, which can be explained within the same framework when being detected by the absorption spectra.
基金supported by the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (NSAF) (Grant No. 10676038)
文摘The filter made up of two gratings performs as a two-dimensional non-spatial filtering. This paper reports that the volume Bragg gratings are fabricated by interfering two collimated coherent laser beams in photopolymer. Diffraction efficiency of a single grating is up to 78% in Bragg＇s condition, then a two-dimensional non-spatial filter, which consists of two volume Bragg gratings and a half-wave plate, enables the laser beam filtered in two dimensions with the diffraction efficiency of 54%. The Bragg＇s condition and effect of polarisation on performances of the two-dimension filter are also discussed.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 20954001 and 10774079)the Natural Science Foundation of Zhejiang Province of China (Grant No. Y7080401)+1 种基金the Natural Science Foundation of Ningbo City (Grant No. 2009A610056)the Startup Fund and K.C. Wong Magna Fund in Ningbo University
文摘The modified dipolar Poisson-Boltzmann （MDPB） equation, where the electrostatics of the dipolar interactions of solvent molecules and also the finite size effects of ions and dipolar solvent molecules are explicitly taken into account on a mean-field level, is studied numerically for a two-plate system with oppositely charged surfaces. The MDPB equation is solved numerically, using the nonlinear Multigrid method, for one-dimensional finite volume meshes. For a high enough surface charge density, numerical results of the MDPB equation reveal that the effective dielectric constant decreases with the increase of the surface charge density. Furthermore, increasing the salt concentration leads to the decrease of the effective dielectric constant close to the charged surfaces. This decrease of the effective dielectric constant with the surface charge density is opposite to the trend from the dipolar Poisson Boltzmann （DPB） equation. This seemingly inconsistent result is due to the fact that the mean-field approach breaks down in such highly charged systems where the counterions and dipoles are strongly attracted to the charged surfaces and form a quasi two-dimensional layer. In the weak-coupling regime with the electrostatic coupling parameter （the ratio of Bjerrum length to Gouy-Chapman length） Ξ 〈 1, where the MDPB equation works, the effective dielectric constant is independent of the distance from the charged surfaces and there is no accumulation of dipoles near the charged surfaces. Therefore, there are no physical and computational advantages for the MDPB equation over the modified Poisson-Boltzmann （MPB） equation where the effect of dipolar interactions of solvent dipoles is implicitly taken into account in the renormalised dielectric constant.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50871029)the National Basic Research Program of China (Grant Nos. 2010CB923401 and 2009CB929501)the Cyanine-Project Foundation of Jiangsu Province of China (Grant No. 1107020060)
文摘Polycrystalline ferroelectric Bi3.25La0.75Ti3O12 thin films are prepared on Pt/Ti/SiO2/Si substrates by the conventional metalorganic decomposition method. It is observed that with the increase of switching pulse width, the remnant polarisation and the coercive field increase. A wider switching pulse can result in poorer fatigue properties, which comes from more charged defects diffusing to and being trapped on domain walls. On the other hand, when the compressive stress is applied to films, the fatigue properties can be improved. This phenomenon is due to the reorientation of domains under stress.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974252,11274376,60978002,and 11179041)the National Basic Research Program of China(Grant No.2010CB922904)+2 种基金the National High Technology Research and Development Program of China(Grant No.2011AA120102)the Natural Science Foundation of Inner Mongolia,China(Grants No.2012MS0101)the Innovation Fund of Inner Mongolia University of Science and Technology,China(Grants No.2010NC064)
文摘We study the electromagnetically-induced transparency（EIT） in a Doppler-broadened cascaded three-level system.We decompose the susceptibility responsible for the EIT resonance into a linear and a nonlinear part, and the EIT resonance reflects mainly the characteristics of the nonlinear susceptibility. It is found that the macroscopic polarization interference effect plays a crucial role in determining the EIT resonance spectrum. To obtain a Doppler-free spectrum there must be polarization interference between atoms of different velocities. A dressed-state model, which analyzes the velocities at which the atoms are in resonance with the dressed states through Doppler frequency shifting, is employed to explain the results.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10774185,10974252,and 10674174)the National Program for Basic Research in China (Grant No. 2006CB921107)
文摘We study phase-conjugate six-wave mixing spectroscopy based on electromagnetically-induced-transparency in a Doppler-broadened folded four-level system. It is found that the six-wave mixing spectrum can be either Doppler-free or very broad, depending on whether the interference between the polarisations of atoms with different velocities is constructive or destructive. To obtain the Doppler-free six-wave mixing spectrum in the folded four-level system, the conditions are more stringent in comparison with those in the cascade and N-type four-level systems. This polarisation interference can be controlled in the presence of a strong coupling field.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10674037)the National Basic Research Program of China (Grant No. 2007CB307001)the program of excellent Team in Harbin Institute of Technology of China
文摘A dual optical tweezers system, which consists of a doughnut mode optical tweezer （DMOT） with the azimuthally polarised trapping beam and a solid mode optical tweezer （SMOT） with the Gauss trapping beam was constructed to compare the axial trapping effect of DMOT and SMOT. The long-distance axial trapping of ST68 microbubbles （MBs） achieved by DMOT was more stable than that of SMOT. Moreover the axial trapping force measured using the viscous drag method, was depended on the diameter of the particle, the laser power, and the numerical aperture （NA） of the objective lens. The measurement of the axial trapping force and the acquisition of CCD images of trapping effect confirmed that the DMOT showed excellent axial trapping ability than SMOT. A simple and effective method is developed to improve axial trapping effect using the azimuthally polarized beam as trapping beam. This is helpful for the long-distance manipulating of particles especially polarised biological objects in axial direction.
基金Project supported by the Natural Science Foundation of Beijing,China (Grant No. 2082006)the National Natural Science Foundation of China (Grant No. 20773073)+1 种基金the Key Grant Project of Chinese Ministry of Education (Grant No. 306020)the Special Research Fund for the Doctoral Program of Higher Education,China (Grant No. 20060003050)
文摘We have studied the temporal bond polarisabilities of para-nitroaniline from the Raman intensities by the algorithm proposed by Wu et al. in 1987 （Tian B, Wu G, Liu G 1987 J. Chem. Phys. 87 7300）. The bond polarisabilities provide much information concerning the electronic structure of the non-resonant Raman excited virtual state. At the initial moment by the 514.5 nm excitation, the tendency of the excited electrons （mapped out by the bond polarisabilities） is to spread to the molecular periphery, and the electronic structure of the Raman virtual state is close to the pseudoquinonoidic state. When the final stage of relaxation is approached, the bond polarisabilities of those peripheral bonds relax faster than those closer to the molecular core, the phenyl ring. The molecule is in the benzenoidic form as demonstrated by the bond polarisabilities after relaxation.
基金Project supported by the National Fundamental Research Program of China (Grant No. 2007CB925204)the National Natural Science Foundation of China (Grant No. 10775048)+1 种基金the Key Project of Chinese Ministry of Education (Grant No. 206103)the Construct Program of the National Key Discipline
文摘We propose a scheme to engineer a non-local two-qubit phase gate between two remote quantum-dot spins. Along with one-qubit local operations, one can in principal perform various types of distributed quantum information processing. The scheme employs a photon with linearly polarisation interacting one after the other with two remote quantum-dot spins in cavities. Due to the optical spin selection rule, the photon obtains a Faraday rotation after the interaction process. By measuring the polarisation of the final output photon, a non-local two-qubit phase gate between the two remote quantum-dot spins is constituted. Our scheme may has very important applications in the distributed quantum information processing.
