Electromagnetic And Acoustic Manipulations And Their Applications In Cloaking And Lensing

Metamaterials have attracted much attentions due to its unique properties different from the natural materials.It has become the cutting edge and the hottest research field of optics,electromagnetics,acoustics,mechanic,materials science and inter-discipline.With the development of transformation optics and transformation acoustics theory,it provides a new route for the regulation of electromagnetic and acoustic waves.Using a coordinate transformation,one can manipulate the propagation of electromagnetic and acoustic wave flexibly.With the help of metamaterials,different types of novel electromagnetic and acoustic devices have been realized.Among them,invisibility cloak and novel lenses are one of the main research directions in the field of electromagnetics and acoustics.At present,there are many technical difficulties in the research of invisibility cloaks.The main obstacle lies in the complex parameters required in the cloak from a traditional coordinate transformation,even with the help of metamaterials.In addition,although the novel lenses designed by coordinate transformation can achieve excellent performance,the function of the lens is limited that can't meet the demand for a multi-functional lens.In view of the above challenges,the content of the dissertation is organized as follows:1.The current acoustic cloaks have complex parameters,making it difficult to achieve a broadband performance.By extending the concept of two dimensional homogeneous coordinate transformation to the acoustic field,we propose a triangular acoustic cloaking device with homogeneous anisotropic parameters,which greatly reduce the difficulty in the practical realization.The acoustic metamaterial unit cells are designed and substituted into the real structure for simulation.The results show that the designed cloak can achieve a broadband invisibility performance for underwater environment.2.Since most of the optical cloaks are limited in two dimensional or quasi-three dimensional cases,we propose the method of polygonal homogenous coordinate transformation for three dimensional cloak design.With a spatial invariant refractive indices discretization,a three dimensional visible light cloaking device is realized with isotropic materials.This device can be effective for full polarized light along multiple directions in three-dimensional perspective,which paves the way for the realization of omni-directional 3D optical cloak in the future.3.As the existing novel acoustic lenses can only achieve single performance,it is difficult to achieve multiple functions in a single lens.We propose the design of a bifunctional acoustic lens using the theory of rotation coordinate transformation.The anisotropic acoustic parameters can be designed to realize different functions for incident acoustic waves in different directions.Using acoustic metamaterials unit cells,a bifunctional acoustic Luneburg-fisheye lens is experimentally verified.Besides,a bifunctional acoustic square lens is also proposed with different focal lengths.Our design will contribute to the realization of multi-functional lens in the future.4.The current monolithic Kerr comb is unable to further manipulate the generated frequency comb signal.We achieve a monolithic lithium niobate photonic circuits for Kerr frequency comb generation and modulation.We also achieve broadband electro-optic frequency comb by designing the dispersion of mirco-ring resonator.Our combs will contribute to monolithic integrated frequency comb solutions for spectroscopy,data communication and so on.