Basing on the necessary condition for the trapping dielectric particle by the Gaussian beam, the Kerr effect in the tweezers with the nonlinear particle or the nonlinear medium is proposed to concern. The expressions ...Basing on the necessary condition for the trapping dielectric particle by the Gaussian beam, the Kerr effect in the tweezers with the nonlinear particle or the nonlinear medium is proposed to concern. The expressions of the optical forces concerned with the Kerr effect, which affects the refractive index of the medium, are presented. The distribution of the optical forces in the trapping region is simulated and discussed. The results show that the stability of the tweezers depends on the nonlinear coefficient of refractive index, and the optical tweezers could be broken down with a critical value of the nonlinear coefficient of refractive index of the surrounding medium, or with a critical value of the laser intensity, duration of laser pulse, and radius of beam waist. Moreover, these results give us the explanation the stability of the optical tweezers used for the trapped object as biological molecule embedded in the fluid, which is sensitive with Kerr effect.展开更多
Owing to the good adjustability and the strong near-field enhancement,surface plasmons are widely used in optical force trap,thus the optical force trap can achieve excellent performance.Here,we use the Laguerre–Gaus...Owing to the good adjustability and the strong near-field enhancement,surface plasmons are widely used in optical force trap,thus the optical force trap can achieve excellent performance.Here,we use the Laguerre–Gaussian beam and a plasmonic gold ring to separate enantiomers by the chiral optical force.Along with the radial optical force that traps the particles,there is also a chirality-sign-sensitive lateral force arising from the optical spin angular momentum,which is caused by the interaction between optical orbit angular momentum and gold ring structure.By selecting a specific incident wavelength,the strong angular scattering and non-chiral related azimuthal optical force can be suppressed.Thus the chiral related azimuthal optical force can induce an opposite orbital rotation of the trapped particles with chirality of different sign near the gold ring.This work proposes an effective approach for catchingand separating chiral enantiomers.展开更多
We show experimentally that when an unfocused continuous wave（CW） laser beam is obliquely incident onto the surface of a millimeter-sized mineral oil drop on sucrose solution, it will exert a pushing force on the oi...We show experimentally that when an unfocused continuous wave（CW） laser beam is obliquely incident onto the surface of a millimeter-sized mineral oil drop on sucrose solution, it will exert a pushing force on the oil drop, making it move forwards along the surface of the sucrose solution. However, after a period of time, the oil drop stops moving. This can be explained as the phenomenon caused by the change of Abraham momentum, the optical gradient force, and friction together.展开更多
We investigate the microscopic optical force density distributions respectively inside a subwavelength-diameter（SD）fiber with flat endface and inside one with oblique endface by using a finite-difference time-domain...We investigate the microscopic optical force density distributions respectively inside a subwavelength-diameter（SD）fiber with flat endface and inside one with oblique endface by using a finite-difference time-domain（FDTD） method.Optical force density distributions at the fiber endfaces can now be readily available. The complete knowledge of optical force density distributions not only reveal features regarding the microscopic near-field optomechanical interaction, but also provide straightforward explanations for the sideway deflections and other mechanical motions. Our results can provide a useful reference for better understanding the mechanical influence when light transports in a microscale or nanoscale structure and for developing future highly-sensitive optomechanical devices.展开更多
In this paper, we develop a theoretical method based on ray optics to calculate the optical force and torque on a metallo-dielectric Janus particle in an optical trap made from a tightly focused Gaussian beam. The Jan...In this paper, we develop a theoretical method based on ray optics to calculate the optical force and torque on a metallo-dielectric Janus particle in an optical trap made from a tightly focused Gaussian beam. The Janus particle is a 2.8 μm diameter polystyrene sphere half-coated with gold thin film several nanometers in thickness. The calculation result shows that the focused beam will push the Janus particle away from the center of the trap,and the equilibrium position of the Janus particle, where the optical force and torque are both zero, is located in a circular orbit surrounding the laser beam axis. The theoretical results are in good agreement qualitatively and quantitatively with our experimental observation. As the ray-optics model is simple in principle, user friendly in formalism, and cost effective in terms of computation resources and time compared with other usual rigorous electromagnetics approaches, the developed theoretical method can become an invaluable tool for understanding and designing ways to control the mechanical motion of complicated microscopic particles in various optical tweezers.展开更多
In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical bea...In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.展开更多
For both the longitudinal binding force and the lateral binding force,a generic way of controlling the mutual attraction and repulsion(usually referred to as reversal of optical binding force)between chiral and plasmo...For both the longitudinal binding force and the lateral binding force,a generic way of controlling the mutual attraction and repulsion(usually referred to as reversal of optical binding force)between chiral and plasmonic hybrid dimers or tetramers has not been reported so far.In this paper,by using a simple plane wave and an onchip configuration,we propose a possible generic way to control the binding force for such hybrid objects in both the near-field region and the far-field region.We also investigate different inter-particle distances while varying the wavelengths of light for each inter-particle distance throughout the investigations.First of all,for the case of longitudinal binding force,we find that chiral-plasmonic hybrid dimer pairs do not exhibit any reversal of optical binding force in the near-field region nor in the far-field region when the wavelength of light is varied in an air medium.However,when the same hybrid system of nanoparticles is placed over a plasmonic substrate,a possible chip,it is possible to achieve a reversal of the longitudinal optical binding force.Later,for the case of lateral optical binding force,we investigate a setup where we place the chiral and plasmonic tetramers on a plasmonic substrate by using two chiral nanoparticles and two plasmonic nanoparticles,with the setup illuminated by a circularly polarized plane wave.By applying the left-handed and the right-handed circular polarization state of light,we also observe the near-field and the far-field reversal of lateral optical binding force for both cases.As far as we know,so far,no work has been reported in the literature on the generic way of reversing the longitudinal optical binding force and the lateral optical binding force of such hybrid objects.Such a generic way of controlling optical binding forces can have important applications in different fields of science and technology in the near future.展开更多
Plasmonic nanocubes are ideal candidates in realizing controllable reflectance surfaces, unidirectional nanoantennas and other plasmon-associated applications. In this work, we perform full-wave calculations of the op...Plasmonic nanocubes are ideal candidates in realizing controllable reflectance surfaces, unidirectional nanoantennas and other plasmon-associated applications. In this work, we perform full-wave calculations of the optical forces in threedimensional gold nanocube dimers. For a fixed center-to-center separation, the rotation of the plasmonic nanocube leads to a slight shift of the plasmonic resonance wavelength and a strong change in the optical binding forces. The effective gap and the near field distribution between the two nanocubes are shown to be crucial to this force variation. We further find that the optical binding force is dominated by the scattering process while the optical forces in the wavevector direction are affected by both scattering and absorption, making the former relatively more sensitive to the rotation of(an effective gap between) the nanocubes. Our results would be useful for building all-optically controllable meta-surfaces.展开更多
We demonstrate that,in a simple linearly-polarized plane wave,the optical pulling forces on nanoparticle clusters with gain can be induced by the Fano-like resonance.The numerical results based on the full-wave calcul...We demonstrate that,in a simple linearly-polarized plane wave,the optical pulling forces on nanoparticle clusters with gain can be induced by the Fano-like resonance.The numerical results based on the full-wave calculation show that the optical pulling forces can be attributed to the recoil forces for the nanoparticle clusters composed of dipolar nanoparticles with three different configurations.Interestingly,the recoil forces giving rise to optical pulling forces are exactly dominated by the coupling term between the electric and magnetic dipoles excited in the nanoparticle clusters,while other higherorder terms have a negligible contribution.In addition,the optical pulling force can be tailored by modulating the Fano-like resonance via either the particle size or the gain magnitude,offering an alternative freedom degree for optical manipulations of particle clusters.展开更多
Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integ...Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.展开更多
Nanostructured dielectric metasurfaces offer unprecedented opportunities to control light-matter momentum exchange,and thereby the forces and torques that light can exert on matter.Here we introduce optical metasurfac...Nanostructured dielectric metasurfaces offer unprecedented opportunities to control light-matter momentum exchange,and thereby the forces and torques that light can exert on matter.Here we introduce optical metasurfaces as components of ultracompact untethered microscopic metaspinners capable of efficient light-induced rotation in a liquid environment.Iluminated by weakly focused light,a metaspinner generates torque via photon recoil through the metasurfaces'ability to bend light towards high angles despite their sub-wavelength thickness,thereby creating orbital angular momentum.We find that a metaspinner is subject to an anomalous transverse lateral optical gradient force that acts in concert with the classical gradient force.Consequently,when two or more metaspinners are trapped together in a laser beam,they collectively orbit the optical axis in the opposite direction to their spinning motion,in stark contrast to rotors coupled through hydrodynamic or mechanical interactions.The metaspinners delineated herein not only serve to llustrate the vast possibilities of utilizing optical metasurfaces for fundamental exploration of optical torques,but they also represent potential building-blocks of artificial active matter systems,light-driven micromachinery,and general-purpose optomechanical devices.展开更多
In this article, the dynamical process of the dielectric particle in the optical tweezer using the counter-propagating Gaussian pulses is investigated by the Langevin equation concerning the Brownian motion. The tempo...In this article, the dynamical process of the dielectric particle in the optical tweezer using the counter-propagating Gaussian pulses is investigated by the Langevin equation concerning the Brownian motion. The temporal stabilities of particle is simulated. The influence of the duration, repetition period and delay time between pulses on stability is discussed.展开更多
The optical manipulation of nanoparticles on superlubricity surfaces was investigated.The research revealed that,due to the near-zero static friction and extremely low dynamic friction at superlubricity interfaces,the...The optical manipulation of nanoparticles on superlubricity surfaces was investigated.The research revealed that,due to the near-zero static friction and extremely low dynamic friction at superlubricity interfaces,the maximum intensity for controlling the optical field can be less than 100 W/cm^(2).The controlled nanoparticle radius can be as small as 5 nm,which is more than one order of magnitude smaller than that of nanoparticles controlled through traditional optical manipulation.Manipulation can be achieved on sub-microsecond to microsecond timescales.Furthermore,the manipulation takes place on solid surfaces and in nonliquid environments,with minimal impact from Brownian motion.By appropriately increasing the dynamic friction,controlling the light intensity,or reducing the pressure,the effects of Brownian motion can be eliminated,allowing for the construction of microstructures with a size as small as 1/75 of the wavelength of light while controlling the light intensity,which is seven orders of magnitude smaller compared to manipulating nanoparticles on traditional surfaces.This enables the control of super-resolution optical microstructures.The optical super-resolution manipulation of nanoparticles on superlubricity surfaces has important applications in fields such as nanofabrication,photolithography,optical metasurfaces,and biochemical analysis.展开更多
Hollow-core fiber(HCF)is a special optical waveguide type that can guide light in the air or liquid core surrounded by properly designed cladding structures.The guiding modes of the fiber can generate sufficient optic...Hollow-core fiber(HCF)is a special optical waveguide type that can guide light in the air or liquid core surrounded by properly designed cladding structures.The guiding modes of the fiber can generate sufficient optical gradient forces to balance the gravity of the particles or confine the atom clouds,forming a stable optical trap in the hollow core.The levitated objects can be propelled over the fiber length along the beam axis through an imbalance of the optical scattering forces or by forming an optical lattice by the counter-propagating beams.The ability to overcome the diffraction of the laser beam in HCF can significantly increase the range of the optical manipulation compared with standard free-space optical tweezers,opening up vast ranges of applications that require long-distance optical control.Since the first demonstration of optical trapping in HCF,hollow-core-fiber-based optical trap(HCF-OT)has become an essential branch of optical tweezer that draws intense research interests.Fast progress on the fundamental principle and applied aspects of HCF-OT has been visible over the past two decades.In recent years,significant milestones in reducing the propagation loss of HCF have been achieved,making HCF an attractive topic in the field of optics and photonics.This further promotes the research and applications of HCF-OT.This review starts from the mechanism of light guidance of HCF,mainly focusing on the issues related to the optical trap in the hollow core.The basic principles and key features of HCF-OT,from optical levitation to manipulation and the detection of macroscopic particles and atoms,are summarized in detail.The key applications of HCF-OT,the challenges and future directions of the technique are also discussed.展开更多
In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not req...In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not require permittivity averaging so that better accuracy can be achieved. Our numerical results on optical force computation show that the standard FDTD method converges linearly, while the proposed method achieves quadratic convergence and better accuracy.展开更多
Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. C...Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.展开更多
Considering the inhomogeneous or heterogeneous background, we have demonstrated that if the background and the half-immersed object are both non-absorbing, the transferred photon momentum to the pulled object can be c...Considering the inhomogeneous or heterogeneous background, we have demonstrated that if the background and the half-immersed object are both non-absorbing, the transferred photon momentum to the pulled object can be considered as the one of Minkowski exactly at the interface. In contrast, the presence of loss inside matter, either in the half-immersed object or in the background, causes optical pushing of the object. Our analysis suggests that for half-immersed plasmonic or lossy dielectric, the transferred momentum of photon can mathematically be modeled as the type of Minkowski and also of Abraham. However, according to a final critical analysis, the idea of Abraham momentum transfer has been rejected. Hence,an obvious question arises: whence the Abraham momentum? It is demonstrated that though the transferred momentum to a half-immersed Mie object(lossy or lossless) can better be considered as the Minkowski momentum, Lorentz force analysis suggests that the momentum of a photon traveling through the continuous background, however, can be modeled as the type of Abraham. Finally, as an interesting sidewalk, a machine learning based system has been developed to predict the time-averaged force within a very short time avoiding time-consuming full wave simulation.展开更多
An experimental method for calibration of optical trap force upon cells by use of electrokinetic phenomena is demonstrated. An electronkinetic sample chamber system （ESCS） is designed instead of a common sample cham...An experimental method for calibration of optical trap force upon cells by use of electrokinetic phenomena is demonstrated. An electronkinetic sample chamber system （ESCS） is designed instead of a common sample chamber and a costly automatism stage, thus the experimental setup is simpler and cheaper. Experiments indicate that the range of the trap force measured by this method is piconewton and sub-piconewton, which makes it fit for study on non-damage interaction between light and biological particles with optical tweezers especially. Since this method is relevant to particle electric charge, by applying an alternating electric field, the new method may overcome the problem of correcting drag force and allow us to measure simultaneously optical trap stiffness and particle electric charge.展开更多
Since the invention of optical tweezers,optical manipulation has advanced significantly in scientific areas such as atomic physics,optics and biological science.Especially in the past decade,numerous optical beams and...Since the invention of optical tweezers,optical manipulation has advanced significantly in scientific areas such as atomic physics,optics and biological science.Especially in the past decade,numerous optical beams and nanoscale devices have been proposed to mechanically act on nanoparticles in increasingly precise,stable and flexible ways.Both the linear and angular momenta of light can be exploited to produce optical tractor beams,tweezers and optical torque from the microscale to the nanoscale.Research on optical forces helps to reveal the nature of light–matter interactions and to resolve the fundamental aspects,which require an appropriate description of momenta and the forces on objects in matter.In this review,starting from basic theories and computational approaches,we highlight the latest optical trapping configurations and their applications in bioscience,as well as recent advances down to the nanoscale.Finally,we discuss the future prospects of nanomanipulation,which has considerable potential applications in a variety of scientific fields and everyday life.展开更多
Light carries energy and momentum,laying the physical foundation of optical manipulation that has facilitated advances in myriad scientific disciplines,ranging from biochemistry and robotics to quantum physics.Utilizi...Light carries energy and momentum,laying the physical foundation of optical manipulation that has facilitated advances in myriad scientific disciplines,ranging from biochemistry and robotics to quantum physics.Utilizing the momentum of light,optical tweezers have exemplified elegant light–matter interactions in which mechanical and optical momenta can be interchanged,whose effects are the most pronounced on micro and nano objects in fluid suspensions.In solid domains,the same momentum transfer becomes futile in the face of dramatically increased adhesion force.Effective implementation of optical manipulation should thereupon switch to the“energy”channel by involving auxiliary physical fields,which also coincides with the irresistible trend of enriching actuation mechanisms beyond sole reliance on light-momentum-based optical force.From this perspective,this review covers the developments of optical manipulation in schemes of both momentum and energy transfer,and we have correspondingly selected representative techniques to present.Theoretical analyses are provided at the beginning of this review followed by experimental embodiments,with special emphasis on the contrast between mechanisms and the practical realization of optical manipulation in fluid and solid domains.展开更多
文摘Basing on the necessary condition for the trapping dielectric particle by the Gaussian beam, the Kerr effect in the tweezers with the nonlinear particle or the nonlinear medium is proposed to concern. The expressions of the optical forces concerned with the Kerr effect, which affects the refractive index of the medium, are presented. The distribution of the optical forces in the trapping region is simulated and discussed. The results show that the stability of the tweezers depends on the nonlinear coefficient of refractive index, and the optical tweezers could be broken down with a critical value of the nonlinear coefficient of refractive index of the surrounding medium, or with a critical value of the laser intensity, duration of laser pulse, and radius of beam waist. Moreover, these results give us the explanation the stability of the optical tweezers used for the trapped object as biological molecule embedded in the fluid, which is sensitive with Kerr effect.
基金Project supported by the National Natural Science Foundation of China (Grant No.12074054)the Fundamental Research Funds for the Central Universities,China (Grant No.DUT21LK06)。
文摘Owing to the good adjustability and the strong near-field enhancement,surface plasmons are widely used in optical force trap,thus the optical force trap can achieve excellent performance.Here,we use the Laguerre–Gaussian beam and a plasmonic gold ring to separate enantiomers by the chiral optical force.Along with the radial optical force that traps the particles,there is also a chirality-sign-sensitive lateral force arising from the optical spin angular momentum,which is caused by the interaction between optical orbit angular momentum and gold ring structure.By selecting a specific incident wavelength,the strong angular scattering and non-chiral related azimuthal optical force can be suppressed.Thus the chiral related azimuthal optical force can induce an opposite orbital rotation of the trapped particles with chirality of different sign near the gold ring.This work proposes an effective approach for catchingand separating chiral enantiomers.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.90921009 and 11274401)
文摘We show experimentally that when an unfocused continuous wave（CW） laser beam is obliquely incident onto the surface of a millimeter-sized mineral oil drop on sucrose solution, it will exert a pushing force on the oil drop, making it move forwards along the surface of the sucrose solution. However, after a period of time, the oil drop stops moving. This can be explained as the phenomenon caused by the change of Abraham momentum, the optical gradient force, and friction together.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11604230 and 11434017)the Guangdong Provincial Innovative and Entrepreneurial Research Team Program,China(Grant No.2016ZT06C594)the National Key Research and Development Program of China(Grant No.2018YFA 0306200)
文摘We investigate the microscopic optical force density distributions respectively inside a subwavelength-diameter（SD）fiber with flat endface and inside one with oblique endface by using a finite-difference time-domain（FDTD） method.Optical force density distributions at the fiber endfaces can now be readily available. The complete knowledge of optical force density distributions not only reveal features regarding the microscopic near-field optomechanical interaction, but also provide straightforward explanations for the sideway deflections and other mechanical motions. Our results can provide a useful reference for better understanding the mechanical influence when light transports in a microscale or nanoscale structure and for developing future highly-sensitive optomechanical devices.
基金supported by the 973 Program of China (no. 2013CB632704)the National Natural Science Foundation of China (no. 11434017)
文摘In this paper, we develop a theoretical method based on ray optics to calculate the optical force and torque on a metallo-dielectric Janus particle in an optical trap made from a tightly focused Gaussian beam. The Janus particle is a 2.8 μm diameter polystyrene sphere half-coated with gold thin film several nanometers in thickness. The calculation result shows that the focused beam will push the Janus particle away from the center of the trap,and the equilibrium position of the Janus particle, where the optical force and torque are both zero, is located in a circular orbit surrounding the laser beam axis. The theoretical results are in good agreement qualitatively and quantitatively with our experimental observation. As the ray-optics model is simple in principle, user friendly in formalism, and cost effective in terms of computation resources and time compared with other usual rigorous electromagnetics approaches, the developed theoretical method can become an invaluable tool for understanding and designing ways to control the mechanical motion of complicated microscopic particles in various optical tweezers.
基金supported by the National 973 Program of China(Nos.2013CB632704 and 2013CB922404)the National Natural Science Foundation of China(Nos.11374357,61475186,and 11434017)
文摘In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.
文摘For both the longitudinal binding force and the lateral binding force,a generic way of controlling the mutual attraction and repulsion(usually referred to as reversal of optical binding force)between chiral and plasmonic hybrid dimers or tetramers has not been reported so far.In this paper,by using a simple plane wave and an onchip configuration,we propose a possible generic way to control the binding force for such hybrid objects in both the near-field region and the far-field region.We also investigate different inter-particle distances while varying the wavelengths of light for each inter-particle distance throughout the investigations.First of all,for the case of longitudinal binding force,we find that chiral-plasmonic hybrid dimer pairs do not exhibit any reversal of optical binding force in the near-field region nor in the far-field region when the wavelength of light is varied in an air medium.However,when the same hybrid system of nanoparticles is placed over a plasmonic substrate,a possible chip,it is possible to achieve a reversal of the longitudinal optical binding force.Later,for the case of lateral optical binding force,we investigate a setup where we place the chiral and plasmonic tetramers on a plasmonic substrate by using two chiral nanoparticles and two plasmonic nanoparticles,with the setup illuminated by a circularly polarized plane wave.By applying the left-handed and the right-handed circular polarization state of light,we also observe the near-field and the far-field reversal of lateral optical binding force for both cases.As far as we know,so far,no work has been reported in the literature on the generic way of reversing the longitudinal optical binding force and the lateral optical binding force of such hybrid objects.Such a generic way of controlling optical binding forces can have important applications in different fields of science and technology in the near future.
基金Project supported by the National Natural Science Foundation of China （Grant Nos. 11004043, 11274083, and 61107036） and the SZMSTP, China （Grant Nos. JC201005260185A, JCYJ20120613114137248, 2011PTZZ048, JC201105160524A, and KQCX20120801093710373）.
文摘Plasmonic nanocubes are ideal candidates in realizing controllable reflectance surfaces, unidirectional nanoantennas and other plasmon-associated applications. In this work, we perform full-wave calculations of the optical forces in threedimensional gold nanocube dimers. For a fixed center-to-center separation, the rotation of the plasmonic nanocube leads to a slight shift of the plasmonic resonance wavelength and a strong change in the optical binding forces. The effective gap and the near field distribution between the two nanocubes are shown to be crucial to this force variation. We further find that the optical binding force is dominated by the scattering process while the optical forces in the wavevector direction are affected by both scattering and absorption, making the former relatively more sensitive to the rotation of(an effective gap between) the nanocubes. Our results would be useful for building all-optically controllable meta-surfaces.
基金Project supported by the Natural Science Foundation of Guangxi Province of China (Grant No.2021GXNSFDA196001)the National Natural Science Foundation of China (Grant Nos.12174076,12074084,and 12204117)+1 种基金Guangxi Science and Technology Project (Grant Nos.AD22080042 and AB21220052)Open Project of State Key Laboratory of Surface Physics in Fudan University (Grant No.KF2022_15)。
文摘We demonstrate that,in a simple linearly-polarized plane wave,the optical pulling forces on nanoparticle clusters with gain can be induced by the Fano-like resonance.The numerical results based on the full-wave calculation show that the optical pulling forces can be attributed to the recoil forces for the nanoparticle clusters composed of dipolar nanoparticles with three different configurations.Interestingly,the recoil forces giving rise to optical pulling forces are exactly dominated by the coupling term between the electric and magnetic dipoles excited in the nanoparticle clusters,while other higherorder terms have a negligible contribution.In addition,the optical pulling force can be tailored by modulating the Fano-like resonance via either the particle size or the gain magnitude,offering an alternative freedom degree for optical manipulations of particle clusters.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60901006 and 11174096)the National Basic Research Program of China(Grant No.2011CB301704)+1 种基金the Program for New Century Excellent Talents in Ministry of Education of China(Grant No.NCET-11-0168)the Foundation for the Author of National Excellent Doctoral Dissertation of China(Grant No.201139)
文摘Integrated optical pulse shaper opens up possibilities for realizing the ultra high-speed and ultra wide-band linear signal processing with compact size and low power consumption. We propose a silicon monolithic integrated optical pulse shaper using optical gradient force, which is based on the eight-path finite impulse response. A cantilever structure is fabricated in one arm of the Mach–Zehnder interferometer（MZI） to act as an amplitude modulator. The phase shift feature of waveguide is analyzed with the optical pump power, and five typical waveforms are demonstrated with the manipulation of optical force. Unlike other pulse shaper schemes based on thermo–optic effect or electro–optic effect, our scheme is based on a new degree of freedom manipulation, i.e., optical force, so no microelectrodes are required on the silicon chip,which can reduce the complexity of fabrication. Besides, the chip structure is suitable for commercial silicon on an insulator（SOI） wafer, which has a top silicon layer of about 220 nm in thickness.
基金Open access funding provided by Chalmers University of Technology.
文摘Nanostructured dielectric metasurfaces offer unprecedented opportunities to control light-matter momentum exchange,and thereby the forces and torques that light can exert on matter.Here we introduce optical metasurfaces as components of ultracompact untethered microscopic metaspinners capable of efficient light-induced rotation in a liquid environment.Iluminated by weakly focused light,a metaspinner generates torque via photon recoil through the metasurfaces'ability to bend light towards high angles despite their sub-wavelength thickness,thereby creating orbital angular momentum.We find that a metaspinner is subject to an anomalous transverse lateral optical gradient force that acts in concert with the classical gradient force.Consequently,when two or more metaspinners are trapped together in a laser beam,they collectively orbit the optical axis in the opposite direction to their spinning motion,in stark contrast to rotors coupled through hydrodynamic or mechanical interactions.The metaspinners delineated herein not only serve to llustrate the vast possibilities of utilizing optical metasurfaces for fundamental exploration of optical torques,but they also represent potential building-blocks of artificial active matter systems,light-driven micromachinery,and general-purpose optomechanical devices.
文摘In this article, the dynamical process of the dielectric particle in the optical tweezer using the counter-propagating Gaussian pulses is investigated by the Langevin equation concerning the Brownian motion. The temporal stabilities of particle is simulated. The influence of the duration, repetition period and delay time between pulses on stability is discussed.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.62174040 and 12174423)the 13th Batch of Outstanding Young Scientific and Technological Talents Project in Guizhou Province(No.[2021]5618)+1 种基金the Science and Technology Projects of Guizhou Provincial(No.ZK[2024]501)the Scientific Research Fund of Guizhou Minzu University(No.GZMUZK[2023]CXTD07).
文摘The optical manipulation of nanoparticles on superlubricity surfaces was investigated.The research revealed that,due to the near-zero static friction and extremely low dynamic friction at superlubricity interfaces,the maximum intensity for controlling the optical field can be less than 100 W/cm^(2).The controlled nanoparticle radius can be as small as 5 nm,which is more than one order of magnitude smaller than that of nanoparticles controlled through traditional optical manipulation.Manipulation can be achieved on sub-microsecond to microsecond timescales.Furthermore,the manipulation takes place on solid surfaces and in nonliquid environments,with minimal impact from Brownian motion.By appropriately increasing the dynamic friction,controlling the light intensity,or reducing the pressure,the effects of Brownian motion can be eliminated,allowing for the construction of microstructures with a size as small as 1/75 of the wavelength of light while controlling the light intensity,which is seven orders of magnitude smaller compared to manipulating nanoparticles on traditional surfaces.This enables the control of super-resolution optical microstructures.The optical super-resolution manipulation of nanoparticles on superlubricity surfaces has important applications in fields such as nanofabrication,photolithography,optical metasurfaces,and biochemical analysis.
基金supported by the National Key Research and Development Program of China(2023YFC3010001)National Natural Science Foundation of China(62275021,62450075,W2412086,62175044,12404315)+1 种基金Beijing Natural Science Foundation(4232078)Science and Technology Innovation Program of Beijing Institute of Technology Teli Students’Science and Technology Innovation Team Project(2024CX06101).
文摘Hollow-core fiber(HCF)is a special optical waveguide type that can guide light in the air or liquid core surrounded by properly designed cladding structures.The guiding modes of the fiber can generate sufficient optical gradient forces to balance the gravity of the particles or confine the atom clouds,forming a stable optical trap in the hollow core.The levitated objects can be propelled over the fiber length along the beam axis through an imbalance of the optical scattering forces or by forming an optical lattice by the counter-propagating beams.The ability to overcome the diffraction of the laser beam in HCF can significantly increase the range of the optical manipulation compared with standard free-space optical tweezers,opening up vast ranges of applications that require long-distance optical control.Since the first demonstration of optical trapping in HCF,hollow-core-fiber-based optical trap(HCF-OT)has become an essential branch of optical tweezer that draws intense research interests.Fast progress on the fundamental principle and applied aspects of HCF-OT has been visible over the past two decades.In recent years,significant milestones in reducing the propagation loss of HCF have been achieved,making HCF an attractive topic in the field of optics and photonics.This further promotes the research and applications of HCF-OT.This review starts from the mechanism of light guidance of HCF,mainly focusing on the issues related to the optical trap in the hollow core.The basic principles and key features of HCF-OT,from optical levitation to manipulation and the detection of macroscopic particles and atoms,are summarized in detail.The key applications of HCF-OT,the challenges and future directions of the technique are also discussed.
基金supported by the Air Force Office of Scientific Research (AFOSR) under Grant numbers FA9550-04-1-0213 and FA9550-07-1-0010
文摘In this paper, we present a nonorthogonal overlapping Yee method for solv- ing Maxwell＇s equations using the diagonal split-cell model. When material interface is presented, the diagonal split-cell model does not require permittivity averaging so that better accuracy can be achieved. Our numerical results on optical force computation show that the standard FDTD method converges linearly, while the proposed method achieves quadratic convergence and better accuracy.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10704031)the National Science Foundation for Fostering Talents in Basic Research of the National Natural Science Foundation of China (Grant No. J0630313)+1 种基金the fundamental Research Fund for Physical and Mathematical of Lanzhou University (Grant No. Lzu05001)the Natural Science Foundation of Gansu,China (Grant No. 3ZS061-A25-035)
文摘Using the algebraic dynamical method, this paper investigates the laser cooling of a moving two-level atom coupled to a cavity field. Analytical solutions of optical forces and the cooling temperatures are obtained. Considering Rb atoms as an example, it finds that the numerical results are relevant to the recent experimental laser cooling investigations.
基金Project supported by the World Academy of Science(TWAS)research grant 2018(Ref:18-121 RG/PHYS/AS I-FR3240303643)North South University(NSU),Bangladesh,internal research grant 2018-19&2019-20(approved by the members of BOT,NSU,Bangladesh)
文摘Considering the inhomogeneous or heterogeneous background, we have demonstrated that if the background and the half-immersed object are both non-absorbing, the transferred photon momentum to the pulled object can be considered as the one of Minkowski exactly at the interface. In contrast, the presence of loss inside matter, either in the half-immersed object or in the background, causes optical pushing of the object. Our analysis suggests that for half-immersed plasmonic or lossy dielectric, the transferred momentum of photon can mathematically be modeled as the type of Minkowski and also of Abraham. However, according to a final critical analysis, the idea of Abraham momentum transfer has been rejected. Hence,an obvious question arises: whence the Abraham momentum? It is demonstrated that though the transferred momentum to a half-immersed Mie object(lossy or lossless) can better be considered as the Minkowski momentum, Lorentz force analysis suggests that the momentum of a photon traveling through the continuous background, however, can be modeled as the type of Abraham. Finally, as an interesting sidewalk, a machine learning based system has been developed to predict the time-averaged force within a very short time avoiding time-consuming full wave simulation.
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60378018 and 60578026.
文摘An experimental method for calibration of optical trap force upon cells by use of electrokinetic phenomena is demonstrated. An electronkinetic sample chamber system （ESCS） is designed instead of a common sample chamber and a costly automatism stage, thus the experimental setup is simpler and cheaper. Experiments indicate that the range of the trap force measured by this method is piconewton and sub-piconewton, which makes it fit for study on non-damage interaction between light and biological particles with optical tweezers especially. Since this method is relevant to particle electric charge, by applying an alternating electric field, the new method may overcome the problem of correcting drag force and allow us to measure simultaneously optical trap stiffness and particle electric charge.
基金support from the National University of Singapore(no.R-263-000-678-133)supported by the Spanish MINECO grants FIS2012-36113-C03-03,FIS2014-55563-REDC and FIS2015-69295-C3-1-P+2 种基金support from the National Natural Science Foundation of China(no.11504252)the Natural Science Foundation for the Youth of Jiangsu Province(no.BK20150306)the Natural Science Foundation for Colleges and Universities in Jiangsu Province of China(no.15KJB140008).
文摘Since the invention of optical tweezers,optical manipulation has advanced significantly in scientific areas such as atomic physics,optics and biological science.Especially in the past decade,numerous optical beams and nanoscale devices have been proposed to mechanically act on nanoparticles in increasingly precise,stable and flexible ways.Both the linear and angular momenta of light can be exploited to produce optical tractor beams,tweezers and optical torque from the microscale to the nanoscale.Research on optical forces helps to reveal the nature of light–matter interactions and to resolve the fundamental aspects,which require an appropriate description of momenta and the forces on objects in matter.In this review,starting from basic theories and computational approaches,we highlight the latest optical trapping configurations and their applications in bioscience,as well as recent advances down to the nanoscale.Finally,we discuss the future prospects of nanomanipulation,which has considerable potential applications in a variety of scientific fields and everyday life.
基金supported by the National Natural Science Foundation of China (Nos.61927820,61905201,and 62275221).
文摘Light carries energy and momentum,laying the physical foundation of optical manipulation that has facilitated advances in myriad scientific disciplines,ranging from biochemistry and robotics to quantum physics.Utilizing the momentum of light,optical tweezers have exemplified elegant light–matter interactions in which mechanical and optical momenta can be interchanged,whose effects are the most pronounced on micro and nano objects in fluid suspensions.In solid domains,the same momentum transfer becomes futile in the face of dramatically increased adhesion force.Effective implementation of optical manipulation should thereupon switch to the“energy”channel by involving auxiliary physical fields,which also coincides with the irresistible trend of enriching actuation mechanisms beyond sole reliance on light-momentum-based optical force.From this perspective,this review covers the developments of optical manipulation in schemes of both momentum and energy transfer,and we have correspondingly selected representative techniques to present.Theoretical analyses are provided at the beginning of this review followed by experimental embodiments,with special emphasis on the contrast between mechanisms and the practical realization of optical manipulation in fluid and solid domains.
