Developing approaches for precise engineering of the optical response of plasmonic nanocavities at the postfabrication stage is important for achieving enhanced and tunable light-matter interactions.In this work,we de...Developing approaches for precise engineering of the optical response of plasmonic nanocavities at the postfabrication stage is important for achieving enhanced and tunable light-matter interactions.In this work,we demonstrate selective enhancement/suppression of specific plasmonic modes by embedding nanocube-on-mirror plasmonic nanocavities into a poly(methyl methacrylate)(PMMA)layer with a controllable thickness.With the increase of the PMMA thickness from 0 to approximately 100 nm,the dominating out-of-plane plasmonic modes are significantly suppressed in the scattering spectra,while the in-plane plasmonic modes are greatly enhanced with a factor reaching 102±20.This enhancement is related to the variation of momentum matching between the plasmonic modes and the radiative fields,affecting both mode excitation and emission properties.In addition,the spectral positions of the in-plane and out-of-plane plasmonic modes shift up to 52±5 and 81±2 nm,respectively.These properties are important for matching and enhancing plasmonic and molecular resonances in a variety of applications.展开更多
Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically ...Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object.In analogy to potential barriers in quantum tunnelling,we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide,thereby achieving a pulling force.Unlike the usual scattering-type optical pulling forces,the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects.In particular,the Einstein-Laub formalism is applied to design this unconventional gradient force.The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide,making it insensitive to absorption.The developed approach helps to break the limitation of scattering forces to obtain longrange optical pulling for manipulation and sorting of nanoparticles and other nano-objects.The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves,such as acoustic or water waves,which are important for numerous applications.展开更多
The optical theorem,which is a consequence of the energy conservation in scattering processes,directly relates the forward scattering amplitude to the extinction cross-section of the object.Originally derived for plan...The optical theorem,which is a consequence of the energy conservation in scattering processes,directly relates the forward scattering amplitude to the extinction cross-section of the object.Originally derived for planar scalar waves,it neglects the complex structure of the focused beams and the vectorial nature of the electromagnetic field.On the other hand,radially or azimuthally polarized fields and various vortex beams,essential in modern photonic technologies,possess a prominent vectorial field structure.Here,we experimentally demonstrate a complete violation of the commonly used form of the optical theorem for radially polarized beams at both visible and microwave frequencies.We show that a plasmonic particle illuminated by such a beam exhibits strong extinction,while the scattering in the forward direction is zero.The generalized formulation of the optical theorem provides agreement with the observed results.The reported effect is vital for the understanding and design of the interaction of complex vector beams carrying longitudinal field components with subwavelength objects important in imaging,communications,nanoparticle manipulation,and detection,as well as metrology.展开更多
基金National Key Research and Development Program of China(2023YFB2806701)National Natural Science Foundation of China(92250305,62305293)+2 种基金Natural Science Foundation of Zhejiang Province(LR25F050001,LDT23F04015F05)Engineering and Physical Sciences Research Council(EP/W017075/1)New Cornerstone Science Foundation(NCI202216)。
文摘Developing approaches for precise engineering of the optical response of plasmonic nanocavities at the postfabrication stage is important for achieving enhanced and tunable light-matter interactions.In this work,we demonstrate selective enhancement/suppression of specific plasmonic modes by embedding nanocube-on-mirror plasmonic nanocavities into a poly(methyl methacrylate)(PMMA)layer with a controllable thickness.With the increase of the PMMA thickness from 0 to approximately 100 nm,the dominating out-of-plane plasmonic modes are significantly suppressed in the scattering spectra,while the in-plane plasmonic modes are greatly enhanced with a factor reaching 102±20.This enhancement is related to the variation of momentum matching between the plasmonic modes and the radiative fields,affecting both mode excitation and emission properties.In addition,the spectral positions of the in-plane and out-of-plane plasmonic modes shift up to 52±5 and 81±2 nm,respectively.These properties are important for matching and enhancing plasmonic and molecular resonances in a variety of applications.
基金Q.D.thanks for the financial support from the Natural Science Foundation of Guangdong Province,China(2019A1515011578)Department of Science and Technology of Guangdong Province,China(2020B1212060067)A.K.and A.Z.work was supported by the ERC iCOMM project(789340).
文摘Optical pulling provides a new degree of freedom in optical manipulation.It is generally believed that long-range optical pulling forces cannot be generated by the gradient of the incident field.Here,we theoretically propose and numerically demonstrate the realization of a long-range optical pulling force stemming from a self-induced gradient field in the manipulated object.In analogy to potential barriers in quantum tunnelling,we use a photonic band gap design in order to obtain the intensity gradients inside a manipulated object placed in a photonic crystal waveguide,thereby achieving a pulling force.Unlike the usual scattering-type optical pulling forces,the proposed gradient-field approach does not require precise elimination of the reflection from the manipulated objects.In particular,the Einstein-Laub formalism is applied to design this unconventional gradient force.The magnitude of the force can be enhanced by a factor of up to 50 at the optical resonance of the manipulated object in the waveguide,making it insensitive to absorption.The developed approach helps to break the limitation of scattering forces to obtain longrange optical pulling for manipulation and sorting of nanoparticles and other nano-objects.The developed principle of using the band gap to obtain a pulling force may also be applied to other types of waves,such as acoustic or water waves,which are important for numerous applications.
基金supported in part by EPSRC(UK)and ERC(project 789340)the support by a TAU Rector Grant and the German-Israeli Foundation(GIF,grant number 2399)support from the Royal Society and the Wolfson Foundation.
文摘The optical theorem,which is a consequence of the energy conservation in scattering processes,directly relates the forward scattering amplitude to the extinction cross-section of the object.Originally derived for planar scalar waves,it neglects the complex structure of the focused beams and the vectorial nature of the electromagnetic field.On the other hand,radially or azimuthally polarized fields and various vortex beams,essential in modern photonic technologies,possess a prominent vectorial field structure.Here,we experimentally demonstrate a complete violation of the commonly used form of the optical theorem for radially polarized beams at both visible and microwave frequencies.We show that a plasmonic particle illuminated by such a beam exhibits strong extinction,while the scattering in the forward direction is zero.The generalized formulation of the optical theorem provides agreement with the observed results.The reported effect is vital for the understanding and design of the interaction of complex vector beams carrying longitudinal field components with subwavelength objects important in imaging,communications,nanoparticle manipulation,and detection,as well as metrology.
