Chinese Physics最新文献

{"title":"Research on spatial frequency shift super-resolution imaging based on evanescent wave illumination","authors":"None Ling Jin-Zhong, None Guo Jin-Kun, None Wang Yu-cheng, None Liu Xin, None Wang Xiao-rui","doi":"10.7498/aps.72.20230934","DOIUrl":"https://doi.org/10.7498/aps.72.20230934","url":null,"abstract":"In spite of the success of fluorescence microscopes (such as STED, STORM and PALM) in biomedical field, which have realized nanometer scale imaging resolution and promoted the great development of bio-medicine, the super-resolution imaging method for non-fluorescent sample is still scarce, and the resolution still has a big gap to nanometer scale. Among existing methods, structured illumination microscopy, PSF engineering, super-oscillatory lens and microsphere assisted nanoscopy are more mature and widely applied. However, limited by the theory itself or engineering practice, the resolution of these approaches is hard to break through 50 nm, which restricts their application in many fields.<br/>Enlightened by synthetic aperture technique, researchers proposed spatial frequency shift super-resolution microscopy through shifting and combining the spatial frequency spectrum of imaging target, which is a promising super-resolution imaging scheme as its resolution limit could be broken through continually. Currently, due to the restriction of the refractive index of optical materials, the wavelength of illumination evanescent wave is hard to be shorten when generated at prism surface via total internal reflection, which determines the highest resolution of this spatial frequency shift super-resolution imaging system. Another deficiency of this scheme is the difference of imaging resolution in different directions, as only in the direction along the wave vector of illumination evanescent wave, the image has the highest resolution; while in the direction perpendicular to it, the image has the lowest resolution, as same as that obtained by far-field illumination.<br/>In order to solve the above thorny questions, a new model for evanescent wave generation has been proposed, which could generate omnidirectional evanescent wave with arbitrary wavelength based the phase modulation of nano-structure, and solve the both problem in imaging system at the same time. To verify the possibility of our scheme, we set up a complete simulation model for spatial frequency shift imaging scheme, which includes three parts:the generation of evanescent wave and its interaction with the nano-structures at imaging target, with could be simulated with FDTD algorithm; the propagation of light field from near-field to far-field, from the sample surface to the focal plane of objective lens, which could be calculated with angular spectrum theory; the propagation of light field from the focal place to the image plane, which could be calculated with Chirp-Z transform.<br/>With this complete simulation model, we compared the resolution of microscopy illuminated by evanescent wave and propagating wave, firstly. The results verified the super-resolution imaging ability of evanescent wave illumination, and also demonstrated the influence of refractive index of prism, as higher refractive index makes shorter wavelength of evanescent wave and higher resolution of spatial frequency shift ","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135356418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spin-polarized transport properties in diluted-magnetic-semiconductor/semiconductor superlattices under light-field assisted","authors":"None Li Chun-Lei, None Zheng Jun, None Wang Xiao-Ming, None Xu Yan","doi":"10.7498/aps.72.20230935","DOIUrl":"https://doi.org/10.7498/aps.72.20230935","url":null,"abstract":"Based on the single electron effective mass approximation theory and the transfer-matrix method, the spin polarized transport properties of electrons in a diluted-magnetic-semiconductor/semiconductor superlattice are studied. The influence of a light-field and a magnetic-field on spin polarized transport and the tunneling time in the superlattice structure are discussed in more detail. The results show that, due to the sp-d electron interaction between conduction band electrons and doped Mn ions, giant Zeeman splitting occurs. It is shown that a significant spin-dependent transmission and the position and width of the resonant-transmission-band of spin-dependent electron can be manipulated by adjusting the magnetic- and light-field. Considering the light field irradiation, the resonance band of electron is deformed and broadened with the increase of the light field intensity. For the case of a strong magnetic field, the transmission coefficient (TC) in the low-energy region is almost zero when the light field is not added, but with the increase of light intensity, the TC increased significantly in the zone increases significantly, that is, a quasi-bound band appears. These features are due to the energy exchange between electrons and the light field when electrons tunnel through the superlattice structure under light irradiation. In addition, light and magnetic fields can significantly change the spin polarization of electrons. Under a certain magnetic field intensity (<i>B</i>=2 T), the light field significantly changes the spin polarization of electrons, the main effect is that the width of the spin polarization platform narrows and oscillatory peaks are accompanied on both sides of the platform. This effect is strengthened with the increase of the light field intensity. However, when the magnetic field is stronger (<i>B</i>=5 T), the opposite is true. These show that the spin polarization can be modulated by the light field. Finally, the tunneling time of spin-up and spin-down electrons is studied by the evolution of Gaussian wave packets in the structure. The results show that the tunneling time depends on a spin of electrons, and it can be seen that the tunneling time of the spin-down electron is shorter than that of the spin-up electron in the superlattice structure. These remarkable properties of spin polarized transport may be beneficial for the devising tunable spin filtering devices based on diluted magnetic semiconductor/semiconductor superlattice structure.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135356420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Edge states and skin effect dependent electron transport properties of a non-Hermitian Su-Schrieffer-Heeger chain","authors":"None Yang Yan-Li, None Duan Zhi-Lei, None Xue Hai-Bin","doi":"10.7498/aps.72.20231286","DOIUrl":"https://doi.org/10.7498/aps.72.20231286","url":null,"abstract":"In the non-reciprocal Su-Schrieffer-Heeger (SSH) chain, the hopping amplitude of an electron in the intra-cell depends on its hopping direction. Consequently, the non-Hermitian SSH chain has both non-trivial topological edge states and non-Hermitian skin effect. However, how to detect the non-trivial topological edge states and non-Hermitian skin effect have become an important topics in non-Hermitian physics. In this paper, we have studied the dependences of the non-trivial topological edge states and the non-Hermitian skin effect of non-Hermitian SSH chain on their electron transport properties in the vicinity of the zero energy. It is demonstrated that when the peak value of the electron transmission probability in the vicinity of the zero energy is much smaller than 1, the non-Hermitian SSH chain has a left-non-Hermitian skin effect; while that in the vicinity of the zero energy is much larger than 1, the non-Hermitian SSH chain has a right-non-Hermitian skin effect. In particular, the skin effect of non-Hermitian SSH chain can be further enhanced in the region of non-trivial topological edge states. Moreover, with increasing the electron tunneling coupling amplitudes between the non-Hermitian SSH chain and the left and right leads from the weak coupling regime to the strong coupling one, the number of the dips of reflection probability in the vicinity of the zero energy will change from two to zero. Therefore, these results theoretically provide an alternative scheme for detecting non-trivial topological edge states and non-Hermitian skin effect types of the non-Hermitian SSH chain.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135551022","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Recent progress on PbTe Majorana nanowires","authors":"None Yang Shuai, None Zhang Hao, None He Ke","doi":"10.7498/aps.72.20231603","DOIUrl":"https://doi.org/10.7498/aps.72.20231603","url":null,"abstract":"Semiconductor-superconductor hybrid nanowire is one of the major platforms for realizing Majorana zero modes (MZMs) and topological quantum computing (TQC), and the III-V InAs and InSb-based nanowires are the most-studied materials in this approach. Despite years of efforts on material improvement and optimization, the too many defects and impurities in the nanowire samples remain the central problem hindering the research progress in the direction. In recent years, a new candidate Majorana nanowire system— IV-VI semiconductor PbTe-superconductor hybrid nanowire—have attracted much attention and witnessed rapid research progress. The unique advantages of PbTe-based nanowires, such as the large dielectric constant and the existence of a lattice-matched substrate, grant them great potential in overcoming the bottleneck problem of sample defects and impurities and becoming an ideal platform to study MZMs and TQC. In this paper, we briefly introduce the recent research progress on selective area growth and transport characterization of in-plane PbTe nanowires and PbTe-superconductor hybrid nanowires, and discuss the advantages and problems of the new candidate Majorana nanowire system, as well as the prospective of realizing TQC based on it.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135758460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Calculation of nucleon scattering on &lt;sup&gt;40&lt;/sup&gt;Ca based on dispersive optical model","authors":"None Zhao Xiu-Niao, None Du Wen-Qing","doi":"10.7498/aps.72.20231054","DOIUrl":"https://doi.org/10.7498/aps.72.20231054","url":null,"abstract":"Spherical nucleus ⁴⁰Ca is important structural and alloy material nucleus. Based on important theoretical value and application prospect of nuclear data of calcium isotopes, nucleon-nucleus scattering data on ⁴⁰Ca nucleus, the main isotopes of natural calcium, are calculated by using dispersive optical model (DOM). The dispersive optical model potential is defined by energy-dependent real potentials, imaginary potentials, and also by the corresponding dispersive contributions to the real potential which are calculated analytically from the corresponding imaginary potentials by using a dispersion relation that follow from the requirement of causality. By fit simultaneously scattering experimental data for neutron and proton, an isospin-dependent dispersive optical model potential containing a dispersive term is derived. This derived potential in this work considers the nonlocality in the real “Hartree-Fock” potential <inline-formula><tex-math id=\"M5\">begin{document}$ V_{rm{HF}} $end{document}</tex-math><alternatives><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20231054_M5.jpg\"/><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20231054_M5.png\"/></alternatives></inline-formula> and introduces the shell gap in the definition of nuclear imaginary volume, surface and spin-orbit potentials near the Fermi energy. This dispersive optical model potential shows a good description of nucleon-nucleus scattering data on ⁴⁰Ca nucleus up to 200 MeV including neutron total cross sections, neutron elastic scattering angular distributions, proton elastic scattering angular distributions, neutron analyzing powers and proton analyzing powers. In addition, the energy dependencies of calculated real volume integrals of dispersive optical model potential is shown, and a typical dispersive hump is seen around the Fermi energy. This dispersive hump behavior naturally obtained from dispersion relations, and allows the dispersion optical potential to get rid of energy dependent geometry, thus avoiding the use of a radius dependent on energy.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental and theoretical study of parallel models for thermoelectric properties of double-layer thermoelectric thin films","authors":"None Yang Shi-Guan, None 孙志刚, None Lin Xin, None He Jun-Song, None Zhai Li-Jun, None Cheng Lin, None Lv Ming Hao, None Liu Hong-Xia, None Sun Zhi-Gang","doi":"10.7498/aps.72.20231259","DOIUrl":"https://doi.org/10.7498/aps.72.20231259","url":null,"abstract":"Currently, the measurement and prediction of the electrical transport performance of thermoelectric double-layer membranes is often based on the theory of parallel modelling, however, the conditions for the use of parallel modelling lack theoretical and experimental support and validation. In this paper, the Seebeck coefficients of Cu/Si and Ag/Si bilayers under applied temperature difference are obtained by using finite element theory simulations with the help of COMSOL Multiphysics software and compared with the parallel model. The effects of whether the ends of the bilayer are plated with a metal Pt layer or not, and the insertion of a high-resistance/low-resistance/insulation interface between the bilayers on the Seebeck coefficient measurements of the bilayer are investigated. It is found that when there is no Pt at the hot and cold ends, the potentials on the Si and Cu sides at the high-resistance and electrically insulating interfaces are uniformly distributed along the direction of the temperature gradient, respectively, and the measured Seebeck coefficients are the same as the value of the material itself, respectively, and the thermal potentials on the Cu side at the low-resistance interfaces vary uniformly with the probe spacing L, while the Si side shows a non-uniform variation. With Pt, the thermal potentials on the Cu and Si sides are uniformly distributed along the direction of the temperature gradient, and the measured values on both Si and Cu sides are the same as the Cu Seebeck coefficients, regardless of the insulating/high-resistance/low-resistance interface. Si/Ag and Bi/Ag bilayers were experimentally investigated. In the absence of Pt, the absolute value of the Seebeck coefficient on the Si side of Si/Ag bilayers decreased with decreasing temperature, but the absolute value of the Seebeck coefficient on the Ag side increased with decreasing temperature. In the presence of Pt, the Seebeck coefficients are the same on both sides of the Bi/Ag bilayer membrane.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dual-mode up/down-conversion optical thermometry of Pr&lt;sup&gt;3+&lt;/sup&gt;-regulated Li&lt;sub&gt;0.9&lt;/sub&gt;K&lt;sub&gt;0.1&lt;/sub&gt;NbO&lt;sub&gt;3&lt;/sub&gt;:Er&lt;sup&gt;3+&lt;/sup&gt; phosphors","authors":"None Jia Chao-Yang, None Yang Xue, None Wang Zhi-Gang, None Chai Rui-Peng, None Pang Qing, None Zhang Xiang-Yu, None Gao Dang-Li","doi":"10.7498/aps.72.20231170","DOIUrl":"https://doi.org/10.7498/aps.72.20231170","url":null,"abstract":"Photothermal sensing is crucial for the development of smart wearable devices. However, designing and synthesizing luminescent materials with suitable multi-wavelength emission and constructing multiple sets of probes in a single material system is a huge challenge for constructing sensitive temperature sensors with a wide temperature range. In this paper, Pr³⁺, Er³⁺ single-doped and double-doped Li_0.9K_0.1NbO₃ phosphors were successfully prepared by high temperature solid phase method, and their structure, morphology, excitation wavelength and temperature-dependent fluorescence properties were characterized by XRD, SEM, fluorescence spectrometer and self-made heating device. Firstly, the photoluminescence of the synthesized series of samples was investigated. The results show that compared with the single-doped Li_0.9K_0.1NbO₃: Er³⁺sample, the up/down-conversion spectra of Pr³⁺, Er³⁺ co-doped phosphors under 808/380 nm excitation show that the green fluorescence emission of Er³⁺ is enhanced. In addition, under 980 nm excitation, Pr³⁺ can effectively regulate the fluorescence energy level population pathway, so that the electrons are more effectively arranged in the ²H_11/2 and ⁴S_3/2 energy levels during the excitation process. The red emission is weakened and the green emission is enhanced, which improves the signal resolution of the fluorescent material and has a significant impact on the optical temperature measurement. Secondly, the up-conversion fluorescence property of Er³⁺ under 808/980 nm laser excitation in Li_0.9K_0.1NbO₃:Er³⁺and Li_0.9K_0.1NbO₃:Pr³⁺,Er³⁺phosphors were investigated. The results show that the red and green fluorescence emissions of Er³⁺ are two-photon processes. Finally, the up/down-conversion dual-mode temperature sensing properties of Er³⁺ in Li_0.9K_0.1NbO₃:Er³⁺ and Li_0.9K_0.1NbO₃:Pr³⁺,Er³⁺ phosphors were investigated. It was found that both materials have good optical temperature measurement performance. Pr³⁺ doping optimizes the dual-mode optical temperature measurement performance of Li_0.9K_0.1NbO₃:Er³⁺ phosphors derived from the thermal coupling energy level of Er³⁺ions. In addition, the up/down-conversion fluorescence mechanism of Li_0.9K_0.1NbO₃:Er³⁺ and Li_0.9K_0.1NbO₃:Er³⁺,Pr³⁺ phosphors is proposed, and the enhanced green fluorescence by Pr³⁺ co-doping is attributed to the energy transfer from Pr³⁺ to Er³⁺ ions, leading ","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"All-optical reservoir computing system based on polarization dynamics","authors":"None Yi You-Jian, None Ding Fu-Cai, None Zhu Ping, None Zhang Dong-Jun, None Liang Xiao, None Sun Mei-Zhi, None Guo Ai-Lin, None Yang Qing-Wei, None Kang Hai-Tao, None Yao Xiu-yu, None Li Zhao-Liang, None Xie Xing-Long, None Zhu Jian-Qiang","doi":"10.7498/aps.72.20230727","DOIUrl":"https://doi.org/10.7498/aps.72.20230727","url":null,"abstract":"The laser probe is one of the main techniques for capturing ultrafast dynamic processes and has extensive applications in fields such as plasma physics, photochemistry, and biomedical science. In this work, a time-wavelength encoded optical probe generation scheme is proposed, which uses cascaded frequency doubling crystals with different phase-matching angles and independent delay lines to achieve time-wavelength encoding. This method offers single-shot high-spatiotemporal resolution, high frame rate, and a wide range of adjustable time windows. The temporal resolution of the optical probe depends on the pulse width of the second harmonic, which can be adjusted by changing the phase-matching angle of the frequency-doubling crystal. The time window of the optical probe is only related to the change in the delay line, which can be adjusted by changing the length of the delay line. Therefore, the time resolution and time window of the optical probe are independent of each other. An optical probe generation system is constructed with 247 fs temporal resolution, 4 μm spatial resolution, 4.05 THz maximal frame rate, and an adjustable time window from sub-picosecond to 3 ns. The three-dimensional spatiotemporal evolution process of plasma filaments is captured within a single shot by using the optical probe. The experimental results show that the ionization front of the plasma propagates forward at a velocity of <inline-formula><tex-math id=\"M2\">begin{document}$ {left(2.963pm 0.024right)times 10}^{8};{rm{m}}/{rm{s}} $end{document}</tex-math><alternatives><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230727_M2.jpg\"/><graphic xmlns:xlink=\"http://www.w3.org/1999/xlink\" xlink:href=\"22-20230727_M2.png\"/></alternatives></inline-formula>, which is consistent with the theoretical prediction. This demonstrates the feasibility of using the probe for capturing ultrafast events. In the part of discussion, we analyze that the key parameters of the optical probe can reach a maximum frame rate of 35.7 THz, a maximum time resolution of 28 fs, and a time window range that can be adjusted from hundreds of femtoseconds to tens of nanoseconds. Finally, the optimal design parameters of the optical probe are given for different application scenarios. The optical probe generation scheme has good scalability and versatility, and can be combined with any wavelength decoding device, diffraction imaging, holographic imaging, tomography scanning, and other technologies. The high spatiotemporal resolution of the optical probe and the independent adjustability of its parameters provide a feasible solution for single-shot high spatiotemporal resolution captures of ultrafast dynamic processes on a multiple time scale.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135402171","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic migration of &lt;100&gt; interstitial dislocation loops under pure W and W containing helium impurity (010) surfaces studied by molecular dynamics simulation","authors":"None Qin Meng-fei, None Wang Ying-Min, None Zhang Hong-Yu, None Sun Ji-Zhong","doi":"10.7498/aps.72.20230651","DOIUrl":"https://doi.org/10.7498/aps.72.20230651","url":null,"abstract":"In the fusion irradiation environment, dislocation loop defects occur under the plasma-facing tungsten surfaces, which affect its mechanical properties and hydrogen/helium retention. This paper presents a study that dynamic behaviors of a <img border=0 > loop with a radius of 1 nm under the W<img border=0 src=\"20230651_O_editing.files/image103.png\"> surface are simulated by using molecular dynamics simulation at the atomic level. It finds that the dislocation loop direction, bulk temperature, depth, and helium atoms have great influence on the motion of the dislocation. This study shows that the <img border=0 src=\"20230651_O_editing.files/image104.png\"> dislocation loop (<img border=0 src=\"20230651_O_editing.files/image105.png\"> is the Burgers vector, <img border=0 src=\"20230651_O_editing.files/image106.png\"> is the surface normal direction) tends to move towards the surface and the <img border=0 > dislocation loop tends to stay in the material. In the course of its migration, the habit plane of dislocation loop may change and the internal stress reduces gradually. The probability of a <img border=0 src=\"20230651_O_editing.files/image104.png\"> dislocation loops escaping from the surface is over 90% when the temperature is higher than 800 K and their initial depth is less than 5 nm. The <img border=0 > dislocation loop can escape from the surface when the temperature is 800 K and the initial depth is less than 2 nm. It is found that <img border=0 src=\"20230651_O_editing.files/image108.png\"> dislocation loops decompose into <img border=0 src=\"20230651_O_editing.files/image109.png\"> dislocations at elevated temperatures. Helium atoms impedes the migration of dislocation loop and increases its retention time. The existence of dislocation loops results in the uneven distribution of helium atoms under the W surface, and will potentially affect the surface morphology of tungsten.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135550504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The asymmetric transmission realized by cascading an acousto-optic device and a whispering gallery mode microcavity","authors":"None Lv Yu-Xi, None Wang Chen, None Duan Tian-Qi, None Zhao Tong, None Chang Peng-Fa, None Wang An-Bang","doi":"10.7498/aps.73.20230653","DOIUrl":"https://doi.org/10.7498/aps.73.20230653","url":null,"abstract":"In this paper, An asymmetric transmission scheme is proposed by cascading an acousto-optic device and a coupled whispering gallery mode (WGM) microsphere cavity, and it is demonstrated by theory and experiment. With the acousto-optic interaction in a fiber, the vector modes of the fundamental core mode could be converted to the different vector modes of a cladding (linear polarization -LP) mode, and because of the optical path difference between the cladding vector modes, the polarization of the cladding mode will be changed. The cladding mode could be converted back to the core fundamental mode by coupling with a WGM microcavity. By calculating the overlapping of the mode fields in the tapered fiber and the microcavity at the resonance wavelength, the coupling coefficients between different LP modes and WGM will be solved. And, the transmittivity and conversion coefficient of the two fiber modes, under the condition that when the polarization of the incident light does not coincide with the polarization orientation of the WGM, can be got. The transmission spectrum of the coupled WGM microcavity is calculated by using MATLAB program under eight states, including the states at different incident directions, different incident polarization of input and whether the acoustic wave is on or off. The results show that the conversion coefficient from the cladding modes to the core mode is completely different from that of the contrary process when the acoustic wave is working. And the forward and backward incident lights have completely different transmission characteristics, thus achieved the asymmetric transmission. The transmittances of forward incidence and reverse incidence at different polarizations are also studied, both of them change periodically over the polarization angle, and their phase difference is equal to the polarization change caused by acousto-optic interaction in the fiber. In the experiment, a two-stage tapered fiber is used to realize the working of acousto-optic interaction and the coupling of whispering gallery mode at the same time. By controlling the working states of the system, the same 8 states as in the calculation had been studied experimentally. In the results, due to the polarization-selection effect of the WGM, the light energy incident from the opposite directions will show different transmission characteristics. While the forward transmittance reaches the maximum value (about 0.505), the reverse transmittance reaches about the minimum value (0.010), and the transmission isolation reaches about 17 dB. The transmittance in two directions was measured at different incident polarization angles, the transmission isolation was analyzed, and the polarization change of cladding mode in the fiber was verified to be about 80°. The measured results coincide with the calculations of the developed theory well. At last, the shortcomings and optimization methods of the scheme are discussed. The asymmetric transmission scheme in this","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202189","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}