The structure of the optical waveguide of 2-bit electrooptic A/D converter with proton-exchange micro prisms is optimized by the finite-difference beam propagation method (FD-BPM). The electrode parameters of the conv...The structure of the optical waveguide of 2-bit electrooptic A/D converter with proton-exchange micro prisms is optimized by the finite-difference beam propagation method (FD-BPM). The electrode parameters of the converter are optimized by conformal mapping. The optimal parameters are a half-wave voltage of (Vπ= 4.5 V) and a bandwidth of (Δf=1.4 GHz).A normalized transmitted power of 69.75% is obtained by FD-BMP and the output waveguide gap is 300 μm.展开更多
While many techniques have been developed for the design of different types of antennas,such as wire antenna,patch antenna,lenses,and reflectors,these cannot be said general-purpose strategies for the synthesis and de...While many techniques have been developed for the design of different types of antennas,such as wire antenna,patch antenna,lenses,and reflectors,these cannot be said general-purpose strategies for the synthesis and design of antennas to achieve the performance characteristics specified by users.Recently,there has been an increasing need for the development of antenna design techniques because of the advent of 5 G and a variety of space,defense,biological,and similar applications,for which a robust and general-purpose design tool is not to be developed.The main objective of this study is to take a look at antenna design from the field manipulation point of view,which has the potential to partially fulfill this need.We review the existing field manipulation techniques,including field transformation methods based on Maxwell’s and wave equations,point out some limitations of these techniques,and then present ways to improve the performance of these methods.Next,we introduce an alternative approach for field manipulation based on two-dimensional(2 D)metasurfaces,and present laws of the generalized reflection and refraction that are based on 2 D surface electromagnetics.Then,we explore how to overcome the limitations of conventional reflection and refraction processes that are strictly bounded by the critical angle.Finally,we provide some application examples of field manipulation methods in the antenna design,with a view on developing a general-purpose strategy for antenna design for future communication.展开更多
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
文摘The structure of the optical waveguide of 2-bit electrooptic A/D converter with proton-exchange micro prisms is optimized by the finite-difference beam propagation method (FD-BPM). The electrode parameters of the converter are optimized by conformal mapping. The optimal parameters are a half-wave voltage of (Vπ= 4.5 V) and a bandwidth of (Δf=1.4 GHz).A normalized transmitted power of 69.75% is obtained by FD-BMP and the output waveguide gap is 300 μm.
基金Project supported by the National Natural Science Foundation of China(No.61971335).
文摘While many techniques have been developed for the design of different types of antennas,such as wire antenna,patch antenna,lenses,and reflectors,these cannot be said general-purpose strategies for the synthesis and design of antennas to achieve the performance characteristics specified by users.Recently,there has been an increasing need for the development of antenna design techniques because of the advent of 5 G and a variety of space,defense,biological,and similar applications,for which a robust and general-purpose design tool is not to be developed.The main objective of this study is to take a look at antenna design from the field manipulation point of view,which has the potential to partially fulfill this need.We review the existing field manipulation techniques,including field transformation methods based on Maxwell’s and wave equations,point out some limitations of these techniques,and then present ways to improve the performance of these methods.Next,we introduce an alternative approach for field manipulation based on two-dimensional(2 D)metasurfaces,and present laws of the generalized reflection and refraction that are based on 2 D surface electromagnetics.Then,we explore how to overcome the limitations of conventional reflection and refraction processes that are strictly bounded by the critical angle.Finally,we provide some application examples of field manipulation methods in the antenna design,with a view on developing a general-purpose strategy for antenna design for future communication.
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.
