The van der Waals force originates from the electromagnetic interaction between quantum fluctuationinduced charges. It is a ubiquitous but subtle force which plays an important role and has a wide range of application...The van der Waals force originates from the electromagnetic interaction between quantum fluctuationinduced charges. It is a ubiquitous but subtle force which plays an important role and has a wide range of applications in surface related phenomena like adhesion, friction,and colloidal stability. Calculating the van der Waals force between closely spaced metallic nanoparticles is very challenging due to the strong concentration of electromagnetic fields at the nanometric gap. Especially, at such a small length scale, the macroscopic description of the dielectric properties no longer suffices. The diffuse nonlocal nature of the induced surface electrons which are smeared out near the boundary has to be considered. Here,we review the recent progress on using three-dimensional transformation optics to study the van der Waals forces between closely spaced nanostructures. Through mapping a seemingly asymmetric system to a more symmetric counterpart, transformation optics enables us to look into the behavior of van der Waals forces at extreme length scales,where the effect of nonlocality is found to dramatically weaken the van der Waals interactions.展开更多
Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applic...Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applications,such as magnet-free nonreciprocity,multimode light shaping,and ultrafast switching.In this review,we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time.We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues,such as topological and non-Hermitian physics.We then extend our discussion to account for spatiotemporal modulation and its applications to nonreciprocity,synthetic motion,giant anisotropy,amplification,and many other effects.Finally,we conclude with a review of the most attractive experimental avenues recently demonstrated and provide a few perspectives on emerging trends for future implementations of time-modulation in photonics.展开更多
基金partially supported by the Gordon and Betty Moore Foundation (J. B. P.)the Royal Commission for the Exhibition of 1851 (R. Z.)+2 种基金the Leverhulme Trust (Y. L. and J. B. P.)the MOE Ac RF Tier 2 (Y. L.)the Program Grant (11235150003) from NTU-A*STAR Silicon Technologies Centre of Excellence (Y. L.)
文摘The van der Waals force originates from the electromagnetic interaction between quantum fluctuationinduced charges. It is a ubiquitous but subtle force which plays an important role and has a wide range of applications in surface related phenomena like adhesion, friction,and colloidal stability. Calculating the van der Waals force between closely spaced metallic nanoparticles is very challenging due to the strong concentration of electromagnetic fields at the nanometric gap. Especially, at such a small length scale, the macroscopic description of the dielectric properties no longer suffices. The diffuse nonlocal nature of the induced surface electrons which are smeared out near the boundary has to be considered. Here,we review the recent progress on using three-dimensional transformation optics to study the van der Waals forces between closely spaced nanostructures. Through mapping a seemingly asymmetric system to a more symmetric counterpart, transformation optics enables us to look into the behavior of van der Waals forces at extreme length scales,where the effect of nonlocality is found to dramatically weaken the van der Waals interactions.
基金funding from the Engineering and Physical Sciences Research Council via an EPSRC Doctoral Prize Fellowship (Grant No. EP/T51780X/1)a Junior Fellowship of the Simons Society of Fellows (855344,EG)+5 种基金funding from Fundação para a Ciência e a Tecnologia and Instituto de Telecomunicações under project UIDB/50008/2020funded by the CEEC Individual program from Fundação para a Ciência e a Tecnologia with reference CEECIND/02947/2020funding from the Engineering and Physical Sciences Research Council (EP/V048880)funding from the Gordon and Betty More Foundationfunding from the Department of Defense, the Simons Foundationthe Air Force Office of Scientific Research MURI program
文摘Time-varying media have recently emerged as a new paradigm for wave manipulation,due to the synergy between the discovery of highly nonlinear materials,such as epsilon-near-zero materials,and the quest for wave applications,such as magnet-free nonreciprocity,multimode light shaping,and ultrafast switching.In this review,we provide a comprehensive discussion of the recent progress achieved with photonic metamaterials whose properties stem from their modulation in time.We review the basic concepts underpinning temporal switching and its relation with spatial scattering and deploy the resulting insight to review photonic time-crystals and their emergent research avenues,such as topological and non-Hermitian physics.We then extend our discussion to account for spatiotemporal modulation and its applications to nonreciprocity,synthetic motion,giant anisotropy,amplification,and many other effects.Finally,we conclude with a review of the most attractive experimental avenues recently demonstrated and provide a few perspectives on emerging trends for future implementations of time-modulation in photonics.
