Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by n...Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrodinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counterrotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distancedependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs.展开更多
We investigate the effects of spontaneously generated coherence(SGC) on both the steady and transient gain properties in a four-level inverted-Y-type atomic system in the presence of a weak probe, two strong coherent ...We investigate the effects of spontaneously generated coherence(SGC) on both the steady and transient gain properties in a four-level inverted-Y-type atomic system in the presence of a weak probe, two strong coherent fields, and an incoherent pump. For the steady process, we find that the inversionless gain mainly origins from SGC. In particular, we can modulate the inversionless gain by changing the relative phase between the two fields. Moreover, the amplitude of the gain peak can be enhanced and the additional gain peak can appear by changing the detuning of the coupling field. As for the transient process, the transient gain properties can also be dramatically affected by the SGC. Compared to the case without SGC,the transient gain can be greatly enhanced with completely eliminated transient absorption by choosing the proper relative phase between the two fields. And the inverted-Y-type system with SGC can be simulated in both atomic and semiconductor quantum well systems avoiding the conditions of SGC.展开更多
Stable dark soliton and dark pulse formation in normally dispersive and red-detuned microcavities are investigated by numerically solving the normalized Lugiato-Lefever equation. The soliton essence is proved by fitti...Stable dark soliton and dark pulse formation in normally dispersive and red-detuned microcavities are investigated by numerically solving the normalized Lugiato-Lefever equation. The soliton essence is proved by fitting the calculated field intensity profile with the analytical formula of a dark soliton. Meanwhile, we find that a dark soliton can be generated either from the nonlinear evolution of an optical shock wave or narrowing of a locally broad dark pulse with smoother fronts. Explicit analytical expression is obtained to describe the oscillatory fronts of the optical shock wave. Furthermore,from the calculation results, we show that for smaller frequency detunings, e.g., α < 3, in addition to the dark soliton formation, a single dark pulse with an oscillatory dip can also arise and propagate stably in the microcavity under proper pump detuning and pump strength combination. The existence region together with various field intensity profiles and the corresponding spectra of single dark pulse are demonstrated.展开更多
Exact solutions of Maxwell's equations describing the lightwave through 3-layer-structured cylindrical waveguide are obtained and the mode field diameter and nonlinear coefficient of air-core nanowires (ACNWs) are...Exact solutions of Maxwell's equations describing the lightwave through 3-layer-structured cylindrical waveguide are obtained and the mode field diameter and nonlinear coefficient of air-core nanowires (ACNWs) are numerically calculated.The simulation results show that ACNWs offer some unique optical properties,such as tight field confining ability and extremely high nonlinearity.At a certain wavelength and air core radius,we optimize the waveguide design to maximize the nonlinear coefficient and minimize the mode field diameter.Our results show that the ACNWs may be powerful potential tools for novel micro-photonic devices in the near future.展开更多
The angle compensation method is adopted to detect sloshing waves by laser diffraction,in the case that the wavelength of the sloshing waves is much greater than that of the incident light.The clear diffraction patter...The angle compensation method is adopted to detect sloshing waves by laser diffraction,in the case that the wavelength of the sloshing waves is much greater than that of the incident light.The clear diffraction pattern is observed to be of asymmetry,involving orders,position and interval of the diffraction spots that are discovered during the light grazing incidence.It is found that the larger the angle of incidence is,the more obvious the asymmetry is.The higher the negative diffraction orders are,the smaller the intervals between spots are.On the contrary,in the positive region,the higher the diffraction orders are,the larger the spot intervals are.The positive interval is larger than that of the same negative diffraction order.If the incident angle reaches 1.558 rad in the experiment,all positive diffraction orders completely vanish.Based on the mechanism of phase modulation and with the Fourier transform method,the relations between the incident angle and position,interval spaces,and orders of diffraction spots are derived theoretically.The theoretical calculations are compared with the experimental data,and the comparison shows that the theoretical calculations are in good agreement with the experimental measurement.展开更多
The structures of pseudo-binary GeS_2–Sb_2S_3, GeS_2–CdS, Sb_2S_3–CdS, and pseudo-ternary GeS_2–Sb_2S_3–CdS chalcogenide systems are systematically investigated by Raman spectroscopy. It is shown that a small num...The structures of pseudo-binary GeS_2–Sb_2S_3, GeS_2–CdS, Sb_2S_3–CdS, and pseudo-ternary GeS_2–Sb_2S_3–CdS chalcogenide systems are systematically investigated by Raman spectroscopy. It is shown that a small number of [S_3Ge–GeS_3]structural units(SUs) and-S-S-/S8 groups exist simultaneously in GeS_2 glass which has a three-dimensional continuous network backbone consisting of cross-linked corner-sharing and edge-sharing [GeS_4] tetrahedra. When Sb_2S_3 is added into GeS_2 glass, the network backbone becomes interconnected [GeS_4] tetrahedra and [SbS_3] pyramids. Moreover, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from Sb_2S_3, leading to the formation of [S_2Sb–SbS_2] SUs. When CdS is added into GeS_2 glass, [Cd_4GeS_6] polyhedra are formed, resulting in a strong crystallization tendency. In addition, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from CdS, resulting in the dissolution of Ge–Ge bond. Co-melting of Sb_2S_3 or CdS with GeS_2 reduces the viscosity of the melt and improves the homogeneity of the glass. The GeS_2 glass can only dissolve up to 10-mol% CdS without crystallization. In comparison, GeS_2–Sb_2S_3 glasses can dissolve up to 20-mol% CdS,implying that Sb_2S_3 could delay the construction of [Cd_4GeS_6] polyhedron and increase the dissolving amount of CdS in the glass.展开更多
A highly reliable interface of self-aligned barrier CuSiN thin layer between the Cu film and the nano-porous SiC:H (p-SiC:H) capping barrier (k=3.3) has been developed in the present work.With the introduction of self...A highly reliable interface of self-aligned barrier CuSiN thin layer between the Cu film and the nano-porous SiC:H (p-SiC:H) capping barrier (k=3.3) has been developed in the present work.With the introduction of self-aligned barrier (SAB) CuSiN between a Cu film and a p-SiC:H capping barrier,the interfacial thermal stability and the adhesion of the Cu/p-SiC:H film are considerably enhanced.A significant improvement of adhesion strength and thermal stability of Cu/p-SiC:H/SiOC:H film stack has been achieved by optimizing the pre-clean step before cap-layer deposition and by forming the CuSiN-like phase.This cap layer on the surface of the Cu can provide a more cohesive interface and effectively suppress Cu atom migration as well.展开更多
A Nd:CLNGG waveguide structure operated at wavelengths of both 632.8 nm and 1539 nm was demonstrated for the first time to our knowledge, which was produced by the 480-keV H^+ion implantation with a dose of 1.0×1...A Nd:CLNGG waveguide structure operated at wavelengths of both 632.8 nm and 1539 nm was demonstrated for the first time to our knowledge, which was produced by the 480-keV H^+ion implantation with a dose of 1.0×10^(17)protons/cm^2.Its propagating modes at 632.8 nm and 1539 nm were measured by the well-known prism coupling technique. The refractive index profile at either 632.8-nm wavelength or 1539-nm wavelength was optical barrier type in the proton-implanted Nd:CLNGG crystal optical waveguide, which was calculated by using the reflectivity calculation method. The near-field light intensity distributions were also simulated by the finite-difference beam propagation method in the visible and nearinfrared bands.展开更多
This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton,the ratio between the soliton pe...This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton,the ratio between the soliton peak intensity and the dark irradiance,is small,the quasi-steady-state soliton width decreases monotonically with the increase of τ,where τ is the parameter correlated with the time,that when the intensity ratio of the soliton is big,the quasi-steady-state soliton width decreases with the increase of τ and then increases with τ,and that the formation time of the steady-state solitons is not correlated with the intensity ratio of the soliton. It finds that the local nonlinear effect increases with the photovoltaic field,which behaves as that the width of soliton beams is small and the self-focusing quasi-period is short. On the other hand,we also discuss that both the time and the temperature have an effect on the beam bending.展开更多
Metasurfaces,with extremely exotic capabilities to manipulate electromagnetic(EM)waves,have derived a plethora of advanced metadevices with intriguing functionalities.Tremendous endeavors have been mainly devoted to t...Metasurfaces,with extremely exotic capabilities to manipulate electromagnetic(EM)waves,have derived a plethora of advanced metadevices with intriguing functionalities.Tremendous endeavors have been mainly devoted to the static metasurfaces and metadevices,where the functionalities cannot be actively tuned in situ post-fabrication.Due to the in-trinsic advantage of active tunability by external stimulus,graphene has been successively demonstrated as a favorable candidate to empower metasurfaces with remarkably dynamic tunability,and their recent advances are propelling the EM wave manipulations to a new height:from static to dynamic.Here,we review the recent progress on dynamic metasur-faces and metadevices enabled by graphene with the focus on electrically-controlled dynamic manipulation of the EM waves covering the mid-infrared,terahertz,and microwave regimes.The fundamentals of graphene,including basic ma-terial properties and plasmons,are first discussed.Then,graphene-empowered dynamic metasurfaces and met-adevices are divided into two categories,i.e.,metasurfaces with building blocks of structured graphene and hybrid metasurfaces integrated with graphene,and their recent advances in dynamic spectrum manipulation,wavefront shap-ing,polarization control,and frequency conversion in near/far fields and global/local ways are elaborated.In the end,we summarize the progress,outline the remaining challenges,and prospect the potential future developments.展开更多
Interdigitated finger capacitance of a continuous-wave terahertz photomixer is calculated using the finite element method.For the frequently used electrode width(0.2 μm) and gap width(1.8 μm),the finger capacitance ...Interdigitated finger capacitance of a continuous-wave terahertz photomixer is calculated using the finite element method.For the frequently used electrode width(0.2 μm) and gap width(1.8 μm),the finger capacitance increases quasi-quadratically with the number of electrodes increasing.The quasi-quadratic dependence can be explained by a sequence of lumped capacitors connected in parallel.For a photomixer composed of 10 electrodes and 9 photoconductive gaps,the finger capacitance increases as the gap width increases at a small electrode width,and follows the reverse trend at a large electrode width.For a constant electrode width,the finger capacitance first decreases and then slightly increases as the gap broadens until the smallest finger capacitance is formed.We also investigate the finger capacitances at different electrode and gap configurations with the 8 μm× 8 μm photomixer commonly used in previous studies.These calculations lead to a better understanding of the finger capacitance affected by the finger parameters,and should lead to terahertz photomixer optimization.展开更多
Optical emission spectra of the plasma generated by a 532 nrn Nd:YAG laser irradiationonto a standard aluminum alloy (E414d) was recorded and analyzed. The electron temperaturewas determined using the Boltzmann plot m...Optical emission spectra of the plasma generated by a 532 nrn Nd:YAG laser irradiationonto a standard aluminum alloy (E414d) was recorded and analyzed. The electron temperaturewas determined using the Boltzmann plot method with three aluminum spectral lines at236.71 nm, 257.509 nm and 308.215 nm, whereas the electron density was inferred by measuringthe Stark broadening line profile of Al(Ⅱ) 281.619 nm. The experimental results confirmed thatthe local thermodynamic equilibrium was valid and the plasma was optically thin. The spectralline intensity increased initially with the increase in laser irradiance and saturated at higher irradiancelevels. Results showed that the energy losses due to the reflection of laser beam fromthe plasma itself were insignificant. The absorption in the plasma through inverse bremsstrahlungand two-photon ionization were studied. At the same time, the variation of transition probabilityratio of Al(Ⅰ) 309.28 nm to Al(Ⅰ) 308.21 nm with laser power density was also studied.展开更多
在交流电场在包含 NR 的飞机使用了的一个 dc 电场和兆兆赫(THz ) 下面的 GaAs nanorings (NR ) 的光吸收理论上被调查。NR 可以围住某磁性的流动面对一磁性对 NR 飞机保持垂直。激子的效果是必要的正确地在 NR 描述光吸收的数字计算表...在交流电场在包含 NR 的飞机使用了的一个 dc 电场和兆兆赫(THz ) 下面的 GaAs nanorings (NR ) 的光吸收理论上被调查。NR 可以围住某磁性的流动面对一磁性对 NR 飞机保持垂直。激子的效果是必要的正确地在 NR 描述光吸收的数字计算表演。应用侧面的 THz 电场，以及 dc 地导致减小，激子山峰拓宽并且切开。与保持的 dc 的存在相对照，重要光吸收山峰在某个频率面对一个 THz 电场在 zero-fieldbandgap 下面产生。光吸收光谱显然取决于应用 THz 地并且在穿 NR 的磁性的流动上的频率和振幅。这为磁电机光的 andTHz 答应 NR 的潜在的应用电镀物品光的察觉到。展开更多
基金Project supported by the Natural Science Foundation of Jilin Province,China (Grant No.20220101016JC)the National Key Research and Development Program of China (Grant No.2022YFE0134200)+1 种基金the National Natural Science Foundation of China (Grant Nos.12174147,91850114,and 11774131)the Open Research Fund of State Key Laboratory of Transient Optics and Photonics。
文摘Molecular-frame photoelectron momentum distributions(MF-PMDs) of an H_(2)^(+) molecule ion in the presence of a pair of counter-rotating circularly polarized attosecond extreme ultraviolet laser pulses is studied by numerically solving the two-dimensional time-dependent Schrodinger equation within the frozen-nuclei approximation. At small time delay, our simulations show that the electron vortex structure is sensitive to the time delay and relative phase between the counterrotating pulses when they are partially overlapped. By adjusting time delay and relative phase, we have the ability to manipulate the MF-PMDs and the appearance of spiral arms. We further show that the internuclear distance can affect the spiral vortices due to its different transition cross sections in the parallel and perpendicular geometries. The lowest-order perturbation theory is employed to interpret these phenomena qualitatively. It is concluded that the internuclear distancedependent transition cross sections and the confinement effect in diatomic molecules are responsible for the variation of vortex structures in the MF-PMDs.
基金Project supported by the National Basic Research Program of China(Grant Nos.2011CB921603 and 2013CB933300)the National Natural Science Foundation of China(Grant Nos.11304308,61076064,and 61176046)+1 种基金Natural Science Foundation of Jilin Province,China(Grant Nos.20140101203JC)the Hundred Talents Program of the Chinese Academy of Sciences
文摘We investigate the effects of spontaneously generated coherence(SGC) on both the steady and transient gain properties in a four-level inverted-Y-type atomic system in the presence of a weak probe, two strong coherent fields, and an incoherent pump. For the steady process, we find that the inversionless gain mainly origins from SGC. In particular, we can modulate the inversionless gain by changing the relative phase between the two fields. Moreover, the amplitude of the gain peak can be enhanced and the additional gain peak can appear by changing the detuning of the coupling field. As for the transient process, the transient gain properties can also be dramatically affected by the SGC. Compared to the case without SGC,the transient gain can be greatly enhanced with completely eliminated transient absorption by choosing the proper relative phase between the two fields. And the inverted-Y-type system with SGC can be simulated in both atomic and semiconductor quantum well systems avoiding the conditions of SGC.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFF0200702)the National Natural Science Foundation of China(Grant Nos.61690222 and 11573058)the CAS-SAFEA International Partnership Program for Creative Research Teams
文摘Stable dark soliton and dark pulse formation in normally dispersive and red-detuned microcavities are investigated by numerically solving the normalized Lugiato-Lefever equation. The soliton essence is proved by fitting the calculated field intensity profile with the analytical formula of a dark soliton. Meanwhile, we find that a dark soliton can be generated either from the nonlinear evolution of an optical shock wave or narrowing of a locally broad dark pulse with smoother fronts. Explicit analytical expression is obtained to describe the oscillatory fronts of the optical shock wave. Furthermore,from the calculation results, we show that for smaller frequency detunings, e.g., α < 3, in addition to the dark soliton formation, a single dark pulse with an oscillatory dip can also arise and propagate stably in the microcavity under proper pump detuning and pump strength combination. The existence region together with various field intensity profiles and the corresponding spectra of single dark pulse are demonstrated.
基金supported by the "Hundreds of Talents Programs" of the Chinese Academy of Sciencesby the National Natural Science Foundation of China (Grant Nos 10874239,10604066 and 60537060)
文摘Exact solutions of Maxwell's equations describing the lightwave through 3-layer-structured cylindrical waveguide are obtained and the mode field diameter and nonlinear coefficient of air-core nanowires (ACNWs) are numerically calculated.The simulation results show that ACNWs offer some unique optical properties,such as tight field confining ability and extremely high nonlinearity.At a certain wavelength and air core radius,we optimize the waveguide design to maximize the nonlinear coefficient and minimize the mode field diameter.Our results show that the ACNWs may be powerful potential tools for novel micro-photonic devices in the near future.
基金Supported by the Open Research Fund of State Key Laboratory of Transient Optics and Photonics of Chinese Academy of Sciences under Grant No SKLST201508the China Postdoctoral Science Foundation Funded Project under Grant No 2015M580945the Government of Chaoyang District Postdoctoral Research Foundation
文摘The angle compensation method is adopted to detect sloshing waves by laser diffraction,in the case that the wavelength of the sloshing waves is much greater than that of the incident light.The clear diffraction pattern is observed to be of asymmetry,involving orders,position and interval of the diffraction spots that are discovered during the light grazing incidence.It is found that the larger the angle of incidence is,the more obvious the asymmetry is.The higher the negative diffraction orders are,the smaller the intervals between spots are.On the contrary,in the positive region,the higher the diffraction orders are,the larger the spot intervals are.The positive interval is larger than that of the same negative diffraction order.If the incident angle reaches 1.558 rad in the experiment,all positive diffraction orders completely vanish.Based on the mechanism of phase modulation and with the Fourier transform method,the relations between the incident angle and position,interval spaces,and orders of diffraction spots are derived theoretically.The theoretical calculations are compared with the experimental data,and the comparison shows that the theoretical calculations are in good agreement with the experimental measurement.
基金supported by the National Natural Science Foundation of China(Grant Nos.61475189,61405240,and 61575086)the Natural Science Basic Research Project in Shaanxi Province,China(Grant No.2015JQ5141)the Jiangsu Key Laboratory of Advanced Laser Materials and Devices,Jiangsu Normal University,China(Grant No.KLALMD-2015-08)
文摘The structures of pseudo-binary GeS_2–Sb_2S_3, GeS_2–CdS, Sb_2S_3–CdS, and pseudo-ternary GeS_2–Sb_2S_3–CdS chalcogenide systems are systematically investigated by Raman spectroscopy. It is shown that a small number of [S_3Ge–GeS_3]structural units(SUs) and-S-S-/S8 groups exist simultaneously in GeS_2 glass which has a three-dimensional continuous network backbone consisting of cross-linked corner-sharing and edge-sharing [GeS_4] tetrahedra. When Sb_2S_3 is added into GeS_2 glass, the network backbone becomes interconnected [GeS_4] tetrahedra and [SbS_3] pyramids. Moreover, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from Sb_2S_3, leading to the formation of [S_2Sb–SbS_2] SUs. When CdS is added into GeS_2 glass, [Cd_4GeS_6] polyhedra are formed, resulting in a strong crystallization tendency. In addition, Ge atoms in[S_3Ge–GeS_3] SUs tend to capture S atoms from CdS, resulting in the dissolution of Ge–Ge bond. Co-melting of Sb_2S_3 or CdS with GeS_2 reduces the viscosity of the melt and improves the homogeneity of the glass. The GeS_2 glass can only dissolve up to 10-mol% CdS without crystallization. In comparison, GeS_2–Sb_2S_3 glasses can dissolve up to 20-mol% CdS,implying that Sb_2S_3 could delay the construction of [Cd_4GeS_6] polyhedron and increase the dissolving amount of CdS in the glass.
基金supported by the National Natural Science Foundation of China(Nos.11075112,61040034)Specialized Research Fund for the Doctoral Program of Higher Education(New Teachers,No.20100181120112)
文摘A highly reliable interface of self-aligned barrier CuSiN thin layer between the Cu film and the nano-porous SiC:H (p-SiC:H) capping barrier (k=3.3) has been developed in the present work.With the introduction of self-aligned barrier (SAB) CuSiN between a Cu film and a p-SiC:H capping barrier,the interfacial thermal stability and the adhesion of the Cu/p-SiC:H film are considerably enhanced.A significant improvement of adhesion strength and thermal stability of Cu/p-SiC:H/SiOC:H film stack has been achieved by optimizing the pre-clean step before cap-layer deposition and by forming the CuSiN-like phase.This cap layer on the surface of the Cu can provide a more cohesive interface and effectively suppress Cu atom migration as well.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11405041 and 61177084)the Nanjing University of Posts and Telecommunications Scientific Foundation(NUPTSF),China(Grant No.NY214159)the RCOCET,China(Grant No.ZSF0401)
文摘A Nd:CLNGG waveguide structure operated at wavelengths of both 632.8 nm and 1539 nm was demonstrated for the first time to our knowledge, which was produced by the 480-keV H^+ion implantation with a dose of 1.0×10^(17)protons/cm^2.Its propagating modes at 632.8 nm and 1539 nm were measured by the well-known prism coupling technique. The refractive index profile at either 632.8-nm wavelength or 1539-nm wavelength was optical barrier type in the proton-implanted Nd:CLNGG crystal optical waveguide, which was calculated by using the reflectivity calculation method. The near-field light intensity distributions were also simulated by the finite-difference beam propagation method in the visible and nearinfrared bands.
基金Project supported by National Nature Science Foundation of China （Grant No 60437020） and the Science and Technology Plan Project of Shannxi Province （Grant No 2004K05-G47）.
基金supported by the National Natural Science Foundation of China (Grant No 10674176)
文摘This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton,the ratio between the soliton peak intensity and the dark irradiance,is small,the quasi-steady-state soliton width decreases monotonically with the increase of τ,where τ is the parameter correlated with the time,that when the intensity ratio of the soliton is big,the quasi-steady-state soliton width decreases with the increase of τ and then increases with τ,and that the formation time of the steady-state solitons is not correlated with the intensity ratio of the soliton. It finds that the local nonlinear effect increases with the photovoltaic field,which behaves as that the width of soliton beams is small and the self-focusing quasi-period is short. On the other hand,we also discuss that both the time and the temperature have an effect on the beam bending.
基金supported by the National Key R&D Program of China (2017YFA0303800)the National Natural Science Foundation of China (61805277, 11634010, 91950207, 11974283, 11774290)+1 种基金the Fundamental Research Funds for the Central Universities (3102017AX009, 3102019PY002, 3102019JC008)the Natural Science Basic Research Program of Shaanxi (2019JQ-447, 2020JM-130)
文摘Metasurfaces,with extremely exotic capabilities to manipulate electromagnetic(EM)waves,have derived a plethora of advanced metadevices with intriguing functionalities.Tremendous endeavors have been mainly devoted to the static metasurfaces and metadevices,where the functionalities cannot be actively tuned in situ post-fabrication.Due to the in-trinsic advantage of active tunability by external stimulus,graphene has been successively demonstrated as a favorable candidate to empower metasurfaces with remarkably dynamic tunability,and their recent advances are propelling the EM wave manipulations to a new height:from static to dynamic.Here,we review the recent progress on dynamic metasur-faces and metadevices enabled by graphene with the focus on electrically-controlled dynamic manipulation of the EM waves covering the mid-infrared,terahertz,and microwave regimes.The fundamentals of graphene,including basic ma-terial properties and plasmons,are first discussed.Then,graphene-empowered dynamic metasurfaces and met-adevices are divided into two categories,i.e.,metasurfaces with building blocks of structured graphene and hybrid metasurfaces integrated with graphene,and their recent advances in dynamic spectrum manipulation,wavefront shap-ing,polarization control,and frequency conversion in near/far fields and global/local ways are elaborated.In the end,we summarize the progress,outline the remaining challenges,and prospect the potential future developments.
基金Supported by the National Natural Science Foundation of China under grant No 10874240, and the Shaanxi Province 13115 Science and Technology Innovative Project under grant No 2008ZDKG-68.
文摘放射状地极化的横梁，由一个高数字的孔(NA ) 集中了客观，在焦点的区域沿着繁殖轴有非繁殖的地，它与线性地极化的横梁比较导致更高轴的套住效率。我们为把一根低顺序的放射状地极化的横梁(R-TEM01 ) 变换成一枚双戒指建议一个图案通过一个特殊设计的极化转子的光线的极化分发(尔泰姆博士) 。这根横梁的二枚戒指的阶段由 p 不同。严密 T 矩阵方法评估的数字结果证明尔泰姆博士横梁能与 R-TEM01 横梁相比改进轴的套住效率，如果套住的粒子的尺寸具有横梁的波长的顺序。[从作者抽象]
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2011AAxxx2008A)Hundred Talent Program of the Chinese Academy of Sciences (Grant No. J08-029)the Main Direction Program of Knowledge Innovation of the Chinese Academy of Sciences (Grant No. YYYJ-1123-4)
文摘Interdigitated finger capacitance of a continuous-wave terahertz photomixer is calculated using the finite element method.For the frequently used electrode width(0.2 μm) and gap width(1.8 μm),the finger capacitance increases quasi-quadratically with the number of electrodes increasing.The quasi-quadratic dependence can be explained by a sequence of lumped capacitors connected in parallel.For a photomixer composed of 10 electrodes and 9 photoconductive gaps,the finger capacitance increases as the gap width increases at a small electrode width,and follows the reverse trend at a large electrode width.For a constant electrode width,the finger capacitance first decreases and then slightly increases as the gap broadens until the smallest finger capacitance is formed.We also investigate the finger capacitances at different electrode and gap configurations with the 8 μm× 8 μm photomixer commonly used in previous studies.These calculations lead to a better understanding of the finger capacitance affected by the finger parameters,and should lead to terahertz photomixer optimization.
基金supported by the Chinese Academy of Sciences/State Administration of Foreign Experts Affairs (CAS/SAFEA) International Partnership Program for Creative Research Teams
文摘Optical emission spectra of the plasma generated by a 532 nrn Nd:YAG laser irradiationonto a standard aluminum alloy (E414d) was recorded and analyzed. The electron temperaturewas determined using the Boltzmann plot method with three aluminum spectral lines at236.71 nm, 257.509 nm and 308.215 nm, whereas the electron density was inferred by measuringthe Stark broadening line profile of Al(Ⅱ) 281.619 nm. The experimental results confirmed thatthe local thermodynamic equilibrium was valid and the plasma was optically thin. The spectralline intensity increased initially with the increase in laser irradiance and saturated at higher irradiancelevels. Results showed that the energy losses due to the reflection of laser beam fromthe plasma itself were insignificant. The absorption in the plasma through inverse bremsstrahlungand two-photon ionization were studied. At the same time, the variation of transition probabilityratio of Al(Ⅰ) 309.28 nm to Al(Ⅰ) 308.21 nm with laser power density was also studied.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10390161 and 30370420.
文摘在交流电场在包含 NR 的飞机使用了的一个 dc 电场和兆兆赫(THz ) 下面的 GaAs nanorings (NR ) 的光吸收理论上被调查。NR 可以围住某磁性的流动面对一磁性对 NR 飞机保持垂直。激子的效果是必要的正确地在 NR 描述光吸收的数字计算表演。应用侧面的 THz 电场，以及 dc 地导致减小，激子山峰拓宽并且切开。与保持的 dc 的存在相对照，重要光吸收山峰在某个频率面对一个 THz 电场在 zero-fieldbandgap 下面产生。光吸收光谱显然取决于应用 THz 地并且在穿 NR 的磁性的流动上的频率和振幅。这为磁电机光的 andTHz 答应 NR 的潜在的应用电镀物品光的察觉到。
基金Project supported by the Major Program of the National Natural Science Foundation of China （Grant No 10390160）, and the National Natural Science Foundation of China （Grant No 30370420）.
