It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and t...It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and theoretically demonstrate that new method can tune the Bragg wavelength without chirp. Further integration of this package can be used for FBG athermal/MEMS packaging.展开更多
Growth of ln0.52Al0.48As epitaxial layers on lnP(100) substrates by molecular beam epitaxy at a wide range of arsenic overpressures (V/III flux ratios from 30 to 300) has been carried out. Analysis performed using low...Growth of ln0.52Al0.48As epitaxial layers on lnP(100) substrates by molecular beam epitaxy at a wide range of arsenic overpressures (V/III flux ratios from 30 to 300) has been carried out. Analysis performed using low-temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) shows a strong and prominent dependence of the PL and XRD linewidths on the V/III flux ratio. Under our growth conditions, both the PL and XRD linewidths exhibit a minimum point at a V/III flux ratio of 150 which corresponds to a maximum in the PL intensity and XRD intensity ratio. Flux ratios exceeding 150 result in an increase in both the PL and XRD linewidths corresponding to a reduction in their associated intensities. Room temperature Raman scattering measurements show a narrowing in the lnAs-like and AlAs-like longitudinal-optic (LO)phonon linewidths which broaden at high flux ratios, while the LO phonon frequencies exhibit a gradual reduction as the flux ratio is increased. PL spectra taken at increasing temperatures show a quenching of the main emission peak followed by the evolution of a broad lower energy emission which is possibly associated with deep lying centres. This effect is more prominent in samples grown at lower V/III flux ratios. Hall effect measurements show a gradual reduction in the mobility in correspondence to an increase in the electron concentration as the flux ratio is increased.展开更多
The manipulation of structured light beams requires simultaneous spatial modulation of amplitude and phase.Based on the double-phase holography(DPH)algorithm,we demonstrate an efficient reconstruction of Bessel beams ...The manipulation of structured light beams requires simultaneous spatial modulation of amplitude and phase.Based on the double-phase holography(DPH)algorithm,we demonstrate an efficient reconstruction of Bessel beams with arbitrary onaxis intensity.Also,the off-axis DPH method enables more than doubled laser energy utilization compared with the widelyused off-axis phase wrapping modulation method.The DPH algorithm is also used in two-photon polymerization to enable the rapid fabrication of microtube arrays,ortho-hexagonal scaffolds,and 2D patterned microstructures.This work gives experimental proof to show the powerful feasibility of the DPH method in constructing economic adaptive laser processing systems.展开更多
On the basis of the stationary phase principle,we construct a family of shaping nondiffracting structured caustic beams with the desired morphology.First,the analytical formula of a nondiffracting astroid caustic is d...On the basis of the stationary phase principle,we construct a family of shaping nondiffracting structured caustic beams with the desired morphology.First,the analytical formula of a nondiffracting astroid caustic is derived theoretically using the stationary phase method.Then,several types of typical desired caustics with different shapes are numerically simulated using the obtained formulas.Hence,the key optical structure and propagation characteristics of nondiffracting caustic beams are investigated.Finally,a designed phase plate and an axicon are used to generate the target light field.The experimental results confirm the theoretical prediction.Compared with the classical method,the introduced method for generating nondiffracting caustic beams is high in light-energy utilization;hence,it is expected to be applied conveniently to scientific experiments.展开更多
In this study,a static shear energy algorithm is presented for the damage assessment of beam-like structures.According to the energy release principle,the strain energy of a damaged element suddenly changes when struc...In this study,a static shear energy algorithm is presented for the damage assessment of beam-like structures.According to the energy release principle,the strain energy of a damaged element suddenly changes when structural damage occurs.Therefore,the change in the static shear energy is employed to determine the damage locations in beam-like structures.The static shear energy is derived from the spectral factorization of the elementary stiffness matrix and structural deflection variation.The advantage of using shear energy as opposed to total energy is that only a few deflection data points of the beam structure are required during the process of damage identification.Another advantage of the proposed approach is that damage detection can be performed without establishing a structural finiteelement model in advance.The proposed technique is first validated using a numerical example with single,multiple,and adjacent damage scenarios.A channel steel beam and rectangular concrete beam are employed as experimental cases to further verify the proposed approach.The results of the simulation and experiment examples indicate that the proposed algorithm provides a simple and effective method for defect localization in beam-like structures.展开更多
We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting...We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.展开更多
The grillage adaptive beam string structure(GABSS)is a new type of smart structure that can self-adjust its deformation and internal forces through a group of active struts(actuators)in response to changes in environm...The grillage adaptive beam string structure(GABSS)is a new type of smart structure that can self-adjust its deformation and internal forces through a group of active struts(actuators)in response to changes in environmental conditions.In this paper,an internal force control method based on a gradient–genetic algorithm(GGA)is proposed for the static control of a tensioned structure(especially the GABSS).Specifically,an optimization model of the GABSS is established in which the adjustment values of the actuators are set as the control variables,and the internal force of the beam is set as the objective function.The improved algorithm has the advantage of the global optimization ability of the genetic algorithm and the local search ability of the gradient algorithm.Two examples are provided to illustrate the application of the GGA method.The results show that the proposed method is practical for solving the internal force control problem of the GABSS.展开更多
Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers ...Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers are a powerful and noninvasive tool for manipulating small objects,and have become indispensable in many fields,including physics,biology,soft condensed matter,among others.In the early days,optical trapping was typically accomplished with a single Gaussian beam.In recent years,we have witnessed rapid progress in the use of structured light beams with customized phase,amplitude,and polarization in optical trapping.Unusual beam properties,such as phase singularities on-axis and propagation invariant nature,have opened up novel capabilities to the study of micromanipulation in liquid,air,and vacuum.We summarize the recent advances in the field of optical trapping using structured light beams.展开更多
Cylindrical vector beams(CVBs),with non-uniform state of polarizations,have become an indispensable tool in many areas of science and technology.However,little research has explored high power CVBs at the femtosecond ...Cylindrical vector beams(CVBs),with non-uniform state of polarizations,have become an indispensable tool in many areas of science and technology.However,little research has explored high power CVBs at the femtosecond regime.In this paper,we report on tne generation of high quality CVBs with high peak power and femtosecond pulse duration in a fiber chirped-pulse amplification laser system.The radially(azimuthally)polarized vector beam has been obtained with a pulse duration of 4A0 fs[430 fs]and a maximum average output power of 20.36 W[20.12 W].The maximum output pulse energy is〜20μJ at a repetition rate of 1 MHz,corresponding to a high peak power of-46 MW.The comparison between simulated intensity profiles and measured experimental results suggests that the generated CVBs have a remarkable intensity distribution.The proposed configuration of our laser system provides a promising solution for high quality CVBs generation with the characteristics of high peak power,ultrashort pulse duration,and high mode purity.展开更多
A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charg...A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However,the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.展开更多
Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially des...Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially designed sandwich such as a microchip laser.The intracavity nonlinear frequency conversion process of a laser beam in a TML state to its second harmonic is theoretically and experimentally investigated,considering different relative phase and weight parameters between the basic modes in the TML beam.Comparison between the far-field SHG beam patterns of fundamental frequency transverse modes in coherently locked and incoherently superposed states demonstrates that the SHG of TML beams can carry more information.Various rarely observed far-field SHG beam patterns are obtained,and they are consistent with the theoretical analysis and numerical simulations.With the obtained SHG beams,the characteristics of the structured fundamental frequency beams can also be conversely investigated or predicted.This work may have important applications in optical 3D printing,optical trapping of particles,and free-space optical communication areas.展开更多
The purpose of this paper is to demonstrate an integrated optimization scheme for a solar-powered drone structure.Consider a primary beam in the wing of large aspect ratio,where 100 lithium batteries are assembled.In ...The purpose of this paper is to demonstrate an integrated optimization scheme for a solar-powered drone structure.Consider a primary beam in the wing of large aspect ratio,where 100 lithium batteries are assembled.In the proposed integrated optimization,the batteries are considered here as parts of the load-carrying structure.The corresponding mechanical behaviors are simulated in the structural design and described with super-elements.The batteries layout and the structural topology are then introduced as mixed design variables and optimized simultaneously to achieve an accordant load-carrying path.Geometrical nonlinearity is considered due to the large deformation.Different periodic structural configurations are tested in the optimization in order to meet the structural manufacturing and assembly convenience.The optimized designs are rebuilt and tested in different load cases.Maintaining the same structural weight,the global mechanical performances are improved greatly compared with the initial design.展开更多
This study proposed a damage identification method compared with the existing ones,based on relative curvature difference and frequency perturbation theory,showing sensitivity to local damage by changes in the curvatu...This study proposed a damage identification method compared with the existing ones,based on relative curvature difference and frequency perturbation theory,showing sensitivity to local damage by changes in the curvature mode and high recognition accuracy of frequencies.Considering the relative curvature difference as a damage index,numerical simulation is used for a simply supported beam under single and multiple damage conditions for different damage degrees.The damage is located according to the curvature mode curves,and the damage degree is qualitatively determined.Based on the perturbation theory,the damage equations are established by the changes between frequencies before and after damage,and the damage localization and degree are verified and determined.Effectiveness of the proposed method for identifying damage at different conditions is numerically investigated.This method potentially promotes the development of damage identification of beam structures.展开更多
文摘It is reported that simple beam structure used for FBG tuning can cause FBG chirping. A novel tuning method utilizing the clamped beam structure under pure bending is introduced. In this paper, we experimentally and theoretically demonstrate that new method can tune the Bragg wavelength without chirp. Further integration of this package can be used for FBG athermal/MEMS packaging.
文摘Growth of ln0.52Al0.48As epitaxial layers on lnP(100) substrates by molecular beam epitaxy at a wide range of arsenic overpressures (V/III flux ratios from 30 to 300) has been carried out. Analysis performed using low-temperature photoluminescence (PL) and double-axis X-ray diffraction (XRD) shows a strong and prominent dependence of the PL and XRD linewidths on the V/III flux ratio. Under our growth conditions, both the PL and XRD linewidths exhibit a minimum point at a V/III flux ratio of 150 which corresponds to a maximum in the PL intensity and XRD intensity ratio. Flux ratios exceeding 150 result in an increase in both the PL and XRD linewidths corresponding to a reduction in their associated intensities. Room temperature Raman scattering measurements show a narrowing in the lnAs-like and AlAs-like longitudinal-optic (LO)phonon linewidths which broaden at high flux ratios, while the LO phonon frequencies exhibit a gradual reduction as the flux ratio is increased. PL spectra taken at increasing temperatures show a quenching of the main emission peak followed by the evolution of a broad lower energy emission which is possibly associated with deep lying centres. This effect is more prominent in samples grown at lower V/III flux ratios. Hall effect measurements show a gradual reduction in the mobility in correspondence to an increase in the electron concentration as the flux ratio is increased.
基金supported by the National Natural Science Foundation of China(Nos.62275191,61605142,and 61827821)the Tianjin Research Program of Application Foundation and Advanced Technology of China(No.17JCJQJC43500)the Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences(Open Fund of the State Key Laboratory of High Field Laser Physics)。
文摘The manipulation of structured light beams requires simultaneous spatial modulation of amplitude and phase.Based on the double-phase holography(DPH)algorithm,we demonstrate an efficient reconstruction of Bessel beams with arbitrary onaxis intensity.Also,the off-axis DPH method enables more than doubled laser energy utilization compared with the widelyused off-axis phase wrapping modulation method.The DPH algorithm is also used in two-photon polymerization to enable the rapid fabrication of microtube arrays,ortho-hexagonal scaffolds,and 2D patterned microstructures.This work gives experimental proof to show the powerful feasibility of the DPH method in constructing economic adaptive laser processing systems.
基金supported by the National Natural Science Foundation of China(No.11974314).
文摘On the basis of the stationary phase principle,we construct a family of shaping nondiffracting structured caustic beams with the desired morphology.First,the analytical formula of a nondiffracting astroid caustic is derived theoretically using the stationary phase method.Then,several types of typical desired caustics with different shapes are numerically simulated using the obtained formulas.Hence,the key optical structure and propagation characteristics of nondiffracting caustic beams are investigated.Finally,a designed phase plate and an axicon are used to generate the target light field.The experimental results confirm the theoretical prediction.Compared with the classical method,the introduced method for generating nondiffracting caustic beams is high in light-energy utilization;hence,it is expected to be applied conveniently to scientific experiments.
基金supported by the National Natural Science Foundation of Zhejiang Province,China(No.LQ20E080013)the Natural Science Foundation of China(Grant No.52008215)+1 种基金the Major Special Science and Technology Project(No.2019B10076)“Ningbo Science and Technology Innovation 2025”and Ningbo Natural Science Foundation Project(No.202003N4169).
文摘In this study,a static shear energy algorithm is presented for the damage assessment of beam-like structures.According to the energy release principle,the strain energy of a damaged element suddenly changes when structural damage occurs.Therefore,the change in the static shear energy is employed to determine the damage locations in beam-like structures.The static shear energy is derived from the spectral factorization of the elementary stiffness matrix and structural deflection variation.The advantage of using shear energy as opposed to total energy is that only a few deflection data points of the beam structure are required during the process of damage identification.Another advantage of the proposed approach is that damage detection can be performed without establishing a structural finiteelement model in advance.The proposed technique is first validated using a numerical example with single,multiple,and adjacent damage scenarios.A channel steel beam and rectangular concrete beam are employed as experimental cases to further verify the proposed approach.The results of the simulation and experiment examples indicate that the proposed algorithm provides a simple and effective method for defect localization in beam-like structures.
基金supported by the National Natural Science Foundation of China(No.11674182)the National Basic Research Program of China(No.2013CB328702)+5 种基金the Tianjin Natural Science Foundation(No.17JCYBJC16700)the 111 Project(No.B07013)the PCSIRT(No.IRT_13R29)the National Research Program of Slovenia(No.P1-0192)the Hundred Young Academic Leaders Program of Nankai Universitythe Collaborative Innovation Center of Extreme Optics,Shanxi University
文摘We develop a new method for smooth and continuous space-variant alignment of the liquid crystal medium in micro-patterned structures, which is based on a radial micro-structured pattern of polymeric ribbons exhibiting out-of-plane orientation with respect to the ITO-coated glass plates. Thanks to the broad range of electrical tunability of the optical retardation for the micro-patterned liquid crystal structures, transformation of the fundamental Gaussian beam into different types of specific beams, including generalized cylindrical vector beams, vortex beams, and vectorial vortex beams, is efficiently demonstrated.
基金supported by the National Key R&D Program of China(No.2017YFC0806100)the National Natural Science Foundation of China(No.51578491)。
文摘The grillage adaptive beam string structure(GABSS)is a new type of smart structure that can self-adjust its deformation and internal forces through a group of active struts(actuators)in response to changes in environmental conditions.In this paper,an internal force control method based on a gradient–genetic algorithm(GGA)is proposed for the static control of a tensioned structure(especially the GABSS).Specifically,an optimization model of the GABSS is established in which the adjustment values of the actuators are set as the control variables,and the internal force of the beam is set as the objective function.The improved algorithm has the advantage of the global optimization ability of the genetic algorithm and the local search ability of the gradient algorithm.Two examples are provided to illustrate the application of the GGA method.The results show that the proposed method is practical for solving the internal force control problem of the GABSS.
基金We thank Professor Kishan Dholakia for his instructive advice and help on the preparation of the manuscript.Y.Y thanks Dr.Leiming Zhou for the helpful discussion.This work was supported by the National Natural Science Foundation of China(11874102 and 61975047)the Sichuan Province Science and Technology Support Program(2020JDRC0006)the Fundamental Research Funds for the Central Universities(ZYGX2019J102).M.C.and Y.A.thank the UK Engineering and Physical Sciences Research Council for funding.
文摘Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers are a powerful and noninvasive tool for manipulating small objects,and have become indispensable in many fields,including physics,biology,soft condensed matter,among others.In the early days,optical trapping was typically accomplished with a single Gaussian beam.In recent years,we have witnessed rapid progress in the use of structured light beams with customized phase,amplitude,and polarization in optical trapping.Unusual beam properties,such as phase singularities on-axis and propagation invariant nature,have opened up novel capabilities to the study of micromanipulation in liquid,air,and vacuum.We summarize the recent advances in the field of optical trapping using structured light beams.
基金This work was supported by the National Natural Science Foundation of China(NSFC)(Nos.61905148,61805278,and 61775146)Equipment Pre-research Field Foundation(No.61404140304)+1 种基金China Postdoctoral Science Foundation(No.2018M633704)State Key Laboratory of Advanced Optical Communication Systems and Networks.
文摘Cylindrical vector beams(CVBs),with non-uniform state of polarizations,have become an indispensable tool in many areas of science and technology.However,little research has explored high power CVBs at the femtosecond regime.In this paper,we report on tne generation of high quality CVBs with high peak power and femtosecond pulse duration in a fiber chirped-pulse amplification laser system.The radially(azimuthally)polarized vector beam has been obtained with a pulse duration of 4A0 fs[430 fs]and a maximum average output power of 20.36 W[20.12 W].The maximum output pulse energy is〜20μJ at a repetition rate of 1 MHz,corresponding to a high peak power of-46 MW.The comparison between simulated intensity profiles and measured experimental results suggests that the generated CVBs have a remarkable intensity distribution.The proposed configuration of our laser system provides a promising solution for high quality CVBs generation with the characteristics of high peak power,ultrashort pulse duration,and high mode purity.
基金This work was supported by the National Natural Science Foundation of China(Nos.62005262 and 51875160)Fundamental Research Funds for the Central Universities(Nos.PA2020GDSK0077 and PA2020GDKC0010)。
文摘A ring-shaped focus, such as a focused vortex beam, has played an important role in microfabrication and optical tweezers.The shape and diameter of the ring-shaped focus can be easily adjusted by the topological charge of the vortex. However,the flow energy is also related to the topological charge, making the individual control of diameter and flow energy of the vortex beam impossible. Meanwhile, the shape of the focus of the vortex beam remains in the hollow ring. Expanding the shape of focus of structural light broadens the applications of the vortex beam in the field of microfabrication. Here, we proposed a ring-shaped focus with controllable gaps by multiplexing the vortex beam and annular beam. The multiplexed beam has several advantages, such as the diameter and flow energy of the focal point can be individually controlled and are not affected by the zero-order beam, and the gap size and position are controllable.
基金the support of the National Natural Science Foundation of China (NSFC) (61805013)
文摘Nonlinear frequency conversion of structured beams has been of great interest recently.We present an intracavity second harmonic generation(SHG)of laser beams in transverse mode locking(TML)states with a specially designed sandwich such as a microchip laser.The intracavity nonlinear frequency conversion process of a laser beam in a TML state to its second harmonic is theoretically and experimentally investigated,considering different relative phase and weight parameters between the basic modes in the TML beam.Comparison between the far-field SHG beam patterns of fundamental frequency transverse modes in coherently locked and incoherently superposed states demonstrates that the SHG of TML beams can carry more information.Various rarely observed far-field SHG beam patterns are obtained,and they are consistent with the theoretical analysis and numerical simulations.With the obtained SHG beams,the characteristics of the structured fundamental frequency beams can also be conversely investigated or predicted.This work may have important applications in optical 3D printing,optical trapping of particles,and free-space optical communication areas.
基金This work is supported by Key Project of Natural Science Foundation of China(Nos.51790171,51761145111,51735005)Natural Science Foundation of China for Excellent Young Scholars(No.11722219).
文摘The purpose of this paper is to demonstrate an integrated optimization scheme for a solar-powered drone structure.Consider a primary beam in the wing of large aspect ratio,where 100 lithium batteries are assembled.In the proposed integrated optimization,the batteries are considered here as parts of the load-carrying structure.The corresponding mechanical behaviors are simulated in the structural design and described with super-elements.The batteries layout and the structural topology are then introduced as mixed design variables and optimized simultaneously to achieve an accordant load-carrying path.Geometrical nonlinearity is considered due to the large deformation.Different periodic structural configurations are tested in the optimization in order to meet the structural manufacturing and assembly convenience.The optimized designs are rebuilt and tested in different load cases.Maintaining the same structural weight,the global mechanical performances are improved greatly compared with the initial design.
基金This study is supported by the National Natural Science Foundation of China under Grant No.51278420the Natural Science Foundation of Shaanxi Province under Grant No.2017JM5021.
文摘This study proposed a damage identification method compared with the existing ones,based on relative curvature difference and frequency perturbation theory,showing sensitivity to local damage by changes in the curvature mode and high recognition accuracy of frequencies.Considering the relative curvature difference as a damage index,numerical simulation is used for a simply supported beam under single and multiple damage conditions for different damage degrees.The damage is located according to the curvature mode curves,and the damage degree is qualitatively determined.Based on the perturbation theory,the damage equations are established by the changes between frequencies before and after damage,and the damage localization and degree are verified and determined.Effectiveness of the proposed method for identifying damage at different conditions is numerically investigated.This method potentially promotes the development of damage identification of beam structures.
