Biphenylene is a new topological material that has attracted much attention recently.By amplifying its size of unit cell,we construct a series of planar structures as homogeneous carbon allotropes in the form of polyp...Biphenylene is a new topological material that has attracted much attention recently.By amplifying its size of unit cell,we construct a series of planar structures as homogeneous carbon allotropes in the form of polyphenylene networks.We first use the low-energy effective model to prove the topological three periodicity for these allotropes.Then,through first-principles calculations,we show that the topological phase has the Dirac point.As the size of per unit cell increases,the influence of the quaternary rings decreases,leading to a reduction in the anisotropy of the system,and the Dirac cone undergoes a transition from type II to type I.We confirm that there are two kinds of non-trivial topological phases with gapless and gapped bulk dispersion.Furthermore,we add a built-in electric field to the gapless system by doping with B and N atoms,which opens a gap for the bulk dispersion.Finally,by manipulating the built-in electric field,the dispersion relations of the edge modes will be transformed into a linear type.These findings provide a hopeful approach for designing the topological carbon-based materials with controllable properties of edge states.展开更多
This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The t...This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.展开更多
In this study, we investigate the acoustic topological insulator or topological metastructure, where an acoustic wave can exist only in an edge or interface state instead of propagating in bulk. Breaking the structura...In this study, we investigate the acoustic topological insulator or topological metastructure, where an acoustic wave can exist only in an edge or interface state instead of propagating in bulk. Breaking the structural symmetry enables the opening of the Dirac cone in the band structure and the generation of a new band gap, wherein a topological edge or interface state emerges.Further, we systematically analyze two types of topological states that stem from the acoustic valley Hall effect mechanism;one type is confined to the boundary, whereas the other type can be observed at the interface between two topologically different structures. Results denote that the selection of different boundaries along with appropriately designed interfaces provides the acoustic waves in the band gap range with abilities of one-way propagation, dual-channel propagation, immunity from backscattering at sharp corners, and/or transition between propagation at interfaces and boundaries. Furthermore, we show that the acoustic wave propagation paths can be tailored in diverse and arbitrary ways by combing the two aforementioned types of topological states.展开更多
The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we s...The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we show that an ultra-broadband edgestate pair in this bandgap can be created using the inverse design by topology optimization.The valley Hall insulator design increases the operational bandwidth 121%compared with an existing valley Hall insulator from recent literature and exhibits extreme field confinement,where more than 99%of the field intensity is concentrated within three unit-cells from the interface.One-way propagation and topological robustness towards small cavity defects are confirmed for the full bandwidth.The exploitation of such edge-state pairs of valley Hall insulators opens an avenue for realizing broadband confined edge modes.In tests for disorder and bend defects,we show that the additional ZIC,with a different operational frequency interval,encountered at the defects,degrades the transmission for bend and disorder defects which may prove significant for the application of VHIs.Through an alternative topology optimization method based on two ZICs,we further increase their common operational bandwidth.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12074156 and 12164023)the Yunnan Local College Applied Basic Research Projects (Grant No.2021Y710)。
文摘Biphenylene is a new topological material that has attracted much attention recently.By amplifying its size of unit cell,we construct a series of planar structures as homogeneous carbon allotropes in the form of polyphenylene networks.We first use the low-energy effective model to prove the topological three periodicity for these allotropes.Then,through first-principles calculations,we show that the topological phase has the Dirac point.As the size of per unit cell increases,the influence of the quaternary rings decreases,leading to a reduction in the anisotropy of the system,and the Dirac cone undergoes a transition from type II to type I.We confirm that there are two kinds of non-trivial topological phases with gapless and gapped bulk dispersion.Furthermore,we add a built-in electric field to the gapless system by doping with B and N atoms,which opens a gap for the bulk dispersion.Finally,by manipulating the built-in electric field,the dispersion relations of the edge modes will be transformed into a linear type.These findings provide a hopeful approach for designing the topological carbon-based materials with controllable properties of edge states.
基金the Nd-glass project from National Major Science and Technology Project of China(No.G-GFZX0205010202.1)the Shanghai International Science&Technology Cooperation Program(No.18590712900)。
文摘This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.
基金supported by the National Natural Science Foundation of China(Grant Nos.11532001,11621062,and 11872329)the Fundamental Research Funds for the Central Universities(Grant No.2016XZZX001-05)the Shenzhen Scientific and Technological Fund for R&D(Grant No.JCYJ20170816172316775)
文摘In this study, we investigate the acoustic topological insulator or topological metastructure, where an acoustic wave can exist only in an edge or interface state instead of propagating in bulk. Breaking the structural symmetry enables the opening of the Dirac cone in the band structure and the generation of a new band gap, wherein a topological edge or interface state emerges.Further, we systematically analyze two types of topological states that stem from the acoustic valley Hall effect mechanism;one type is confined to the boundary, whereas the other type can be observed at the interface between two topologically different structures. Results denote that the selection of different boundaries along with appropriately designed interfaces provides the acoustic waves in the band gap range with abilities of one-way propagation, dual-channel propagation, immunity from backscattering at sharp corners, and/or transition between propagation at interfaces and boundaries. Furthermore, we show that the acoustic wave propagation paths can be tailored in diverse and arbitrary ways by combing the two aforementioned types of topological states.
基金supported by the China Scholarship Council(CSC)the Danmarks Grundforskningsfond(Grant No.DNRF147)。
文摘The existence of a single topologically protected edge state in the first bulk bandgap for acoustic/elastic valley Hall insulators(VHIs)with zigzag interface configurations(ZICs)is well known.However,in this work,we show that an ultra-broadband edgestate pair in this bandgap can be created using the inverse design by topology optimization.The valley Hall insulator design increases the operational bandwidth 121%compared with an existing valley Hall insulator from recent literature and exhibits extreme field confinement,where more than 99%of the field intensity is concentrated within three unit-cells from the interface.One-way propagation and topological robustness towards small cavity defects are confirmed for the full bandwidth.The exploitation of such edge-state pairs of valley Hall insulators opens an avenue for realizing broadband confined edge modes.In tests for disorder and bend defects,we show that the additional ZIC,with a different operational frequency interval,encountered at the defects,degrades the transmission for bend and disorder defects which may prove significant for the application of VHIs.Through an alternative topology optimization method based on two ZICs,we further increase their common operational bandwidth.
