As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular mom...As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.展开更多
The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe...The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems.Due to the lack of suitable fusion neutron testing facilities,we have to rely on ion irradiation experiments to test candidate materials in fusion reactors.Moreover,fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen.One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams(MSIB)irradiation that has been studied for decades.To date,there is no convincing conclusion on these He-H synergistic effects among these experiments.Recently,a multiple ion beam in-situ transmission electron microscopy(TEM)analysis facility was developed in Xiamen University(XIAMEN facility),which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China.In this work,we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility.The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual-and single-ion beam(s)irradiated steels.Synergistic effects were observed in MSIB irradiated steels.Helium was found to be critical for cavity formation,while hydrogen has strong synergistic effect on increasing swelling.展开更多
Intense vortex beam is expected to empower captivating phenomena and applications in high power laser-matter interac-tions.Currently,the superposition of multiple vortex beams has shown the unique ability to tailor an...Intense vortex beam is expected to empower captivating phenomena and applications in high power laser-matter interac-tions.Currently,the superposition of multiple vortex beams has shown the unique ability to tailor and enhance the vortex field.However,traditional strategies to generate such beams suffer from large volume or/and low laser-induced damage threshold,hindering the practical widespread applications.Herein,a single high-threshold metasurface is proposed and experimentally demonstrated for the generation and superposition of multiple collinear vortex beams.This scheme takes advantage of the high conversion efficiency of phase-only modulation in the metasurface design by adopting the concept of a sliced phase pattern in the azimuthal direction.An optical hot spot with an enhanced intensity and steady spatial propagation is experimentally achieved.Moreover,femtosecond laser-induced birefringent nanostructures embedded in silica glass are utilized as the building block with high optical efficiency.Transmittance greater than 99.4%in the near-in-frared range and laser-induced damage threshold as high as 68.0 J/cm^(2)(at 1064 nm,6 ns)are experimentally verified.Considering these remarkable performances,the demonstrated high-threshold metasurface has promising applications in a host of high-power laser fields.展开更多
Benefiting from the unprecedented superiority of coding metasurfaces at manipulating electromagnetic waves in the microwave band,in this paper,we use the Pancharatnam-Berry(PB)phase concept to propose a high-efficienc...Benefiting from the unprecedented superiority of coding metasurfaces at manipulating electromagnetic waves in the microwave band,in this paper,we use the Pancharatnam-Berry(PB)phase concept to propose a high-efficiency reflectivetype coding metasurface that can arbitrarily manipulate the scattering pattern of terahertz waves and implement many novel functionalities.By optimizing the coding sequences,we demonstrate that the designed 1-,2-,and 3-bit coding metasurfaces with specific coding sequences have the strong ability to control reflected terahertz waves.The two proposed1-bit coding metasurfaces demonstrate that the reflected terahertz beam can be redirected and arbitrarily controlled.For normally incident x-and y-polarized waves,a 10 d B radar cross-section(RCS)reduction can be achieved from 2.1 THz to5.2 THz using the designed 2-bit coding metasurface.Moreover,two kinds of orbital angular momentum(OAM)vortex beams with different moduli are generated by a coding metasurface using different coding sequences.Our research provides a new degree of freedom for the sophisticated manipulation of terahertz waves,and contributes to the development of metasurfaces towards practical applications.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11474166 and 11604156)the Science and Technology Cooperation Projects of People’s Republic of China–Romania(Grant No.42-23)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20161013)the Postdoctoral Science Foundation of China(Grant No.2016M591874)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘As a kind of special acoustic field, the helical wavefront of an acoustic vortex（AV） beam is demonstrated to have a pressure zero with phase singularity at the center in the transverse plane. The orbital angular momentum of AVs can be applied to the field of particle manipulation, which attracts more and more attention in acoustic researches. In this paper,by using the simplified circular array of point sources, dual coaxial AV beams are excited by the even-and odd-numbered sources with the topological charges of l_E and l_O based on the phase-coded approach, and the composite acoustic field with an on-axis center-AV and multiple off-axis sub-AVs can be generated by the superimposition of the AV beams for｜l_E｜ ≠ ｜l_O｜. The generation of edge phase dislocation is theoretically derived and numerically analyzed for l_E=-l_O. The numbers and the topological charges as well as the locations of the center-AV and sub-AVs are demonstrated, which are proved to be determined by the topological charges of the coaxial AV beams. The proposed approach breaks through the limit of only one on-axis AV with a single topological charge along the beam axis, and also provides the feasibility of off-axis particle trapping with multiple AVs in object manipulation.
基金Project supported by the National Natural Science Foundation of China(Grant No.11935004).
文摘The development of reliable fusion energy is one of the most important challenges in this century.The accelerated degradation of structural materials in fusion reactors caused by neutron irradiation would cause severe problems.Due to the lack of suitable fusion neutron testing facilities,we have to rely on ion irradiation experiments to test candidate materials in fusion reactors.Moreover,fusion neutron irradiation effects are accompanied by the simultaneous transmutation production of helium and hydrogen.One important method to study the He-H synergistic effects in materials is multiple simultaneous ion beams(MSIB)irradiation that has been studied for decades.To date,there is no convincing conclusion on these He-H synergistic effects among these experiments.Recently,a multiple ion beam in-situ transmission electron microscopy(TEM)analysis facility was developed in Xiamen University(XIAMEN facility),which is the first triple beam system and the only in-running in-situ irradiation facility with TEM in China.In this work,we conducted the first high-temperature triple simultaneous ion beams irradiation experiment with TEM observation using the XIAMEN facility.The responses to in-situ triple-ion beams irradiation in austenitic steel 304L SS and ferritic/martensitic steel CLF-1 were studied and compared with the results in dual-and single-ion beam(s)irradiated steels.Synergistic effects were observed in MSIB irradiated steels.Helium was found to be critical for cavity formation,while hydrogen has strong synergistic effect on increasing swelling.
基金financial supports from the National Key Research and Development Program(Grant No.2018YFA0701800)the National Natural Science Foundation of China(NSFC)(Grant No.62192773)the West Light Foundation of Chinese Academy of Sciences(Grant No.xbzg-zdsys-202307).
文摘Intense vortex beam is expected to empower captivating phenomena and applications in high power laser-matter interac-tions.Currently,the superposition of multiple vortex beams has shown the unique ability to tailor and enhance the vortex field.However,traditional strategies to generate such beams suffer from large volume or/and low laser-induced damage threshold,hindering the practical widespread applications.Herein,a single high-threshold metasurface is proposed and experimentally demonstrated for the generation and superposition of multiple collinear vortex beams.This scheme takes advantage of the high conversion efficiency of phase-only modulation in the metasurface design by adopting the concept of a sliced phase pattern in the azimuthal direction.An optical hot spot with an enhanced intensity and steady spatial propagation is experimentally achieved.Moreover,femtosecond laser-induced birefringent nanostructures embedded in silica glass are utilized as the building block with high optical efficiency.Transmittance greater than 99.4%in the near-in-frared range and laser-induced damage threshold as high as 68.0 J/cm^(2)(at 1064 nm,6 ns)are experimentally verified.Considering these remarkable performances,the demonstrated high-threshold metasurface has promising applications in a host of high-power laser fields.
基金Project supported by the National Natural Science Foundation of China(Grant No.61865008)Northwest Normal University Young Teachers’Scientific Research Capability Upgrading Program(Grant No.NWNU-LKQN2020-11)the Scientific Research Fund of Sichuan Provincial Science and Technology Department,China(Grant No.2020YJ0137)。
文摘Benefiting from the unprecedented superiority of coding metasurfaces at manipulating electromagnetic waves in the microwave band,in this paper,we use the Pancharatnam-Berry(PB)phase concept to propose a high-efficiency reflectivetype coding metasurface that can arbitrarily manipulate the scattering pattern of terahertz waves and implement many novel functionalities.By optimizing the coding sequences,we demonstrate that the designed 1-,2-,and 3-bit coding metasurfaces with specific coding sequences have the strong ability to control reflected terahertz waves.The two proposed1-bit coding metasurfaces demonstrate that the reflected terahertz beam can be redirected and arbitrarily controlled.For normally incident x-and y-polarized waves,a 10 d B radar cross-section(RCS)reduction can be achieved from 2.1 THz to5.2 THz using the designed 2-bit coding metasurface.Moreover,two kinds of orbital angular momentum(OAM)vortex beams with different moduli are generated by a coding metasurface using different coding sequences.Our research provides a new degree of freedom for the sophisticated manipulation of terahertz waves,and contributes to the development of metasurfaces towards practical applications.
