Transformation Optics:Approaching Practical Design Of Cloaking,Nanoimaging And Nanofocusing

Optical devices including invisibility cloak and optical black hole,the stuff of science fiction for ages,now turned into a scientific reality thanks to the pioneering theoretical works in transformation optics in 2006 proposed by Pendry.During these years,scientists made a lot of efforts to improve the transformation optics theory and it becomes one of the most important design approaches in optics and nanophotonics.A new era of optical devices based on transformation optics was started.This dissertation addressed the design and implementation of optical invisibility cloak,nanoimaging and nanofocusing based on transformation optics theory.In the first part of the dissertation,we introduce the research background of optical invisibility cloak,nanoimaging and nanofocusing.The metamaterial unit cell for realizing perfect optical devices is difficult to fabricate based on the state of the art nanotechnology.In this regard,people could only figure out optical devices with limited performance,which may contain seveal drawbacks involving small structural dimension,narrow working frequency range,sensitivity to material loss and so on.The main work of this dissertation is detailed as follows:1.Most of the optical cloaks have very small hidden region.By combining both coordinate transformation and conformal mapping methods,we propose an original approach for designing large-scale invisibility cloak,which is not related to anisotropic factor.According to this approach,we experimentally demonstrate the first,large-scale,far-infrared,unidirectional invisibility cloak which could be utilized to evade thermal detection.2.We present a lens design which has the ability to accomplish the dark-field nanoimaging.This lens consists of type ? and type ? hyperbolic metamaterials that remove low-k field waves and manipulate only high-k field waves,in order to enhance the image contrast.3.By combining imaginary coordinate and folded-geometry transformations,we propose an alternative method for broadband nanoimaging in order to overcome the bandwidth limitations of conventional lenses.The anomalous dispersion for different operational wavelengths allows for matching invariable propagation direction of high-k field waves and dramatically broadens the bandwidth of the lenslet.4.In order to solve the complicated nanofabrication problems during lens design process,we utilize two-dimensional materials to achieve the nanoimaging instead of using the noble metals.Since the optical properties of the graphene will not change after bending,stretching and stacking due to the weak interaction between monolayer graphene in the ultraviolet spectrum,the designed lens will be flexible and easy to be fabricated.5.Moving nanofocusing techniques beyond proof-of-principle concepts to technologically relevant implementations still remains a challenge.To solve this problem,we report the design of a high-throughput gradient hyperbolic lenslet This efficient design is achieved through high-order transformation optics,imaginary coordinate transformation and circular effective-medium theory,which are used to engineer the radially varying anisotropic artificial material based on thin alternating cylindrical layers of metal and dielectric.6.To overcome the geometrical singularities in plasmonic light nanostructures,we propose to utilize cylindrical nanostructure with hyperbolic dispersion.Optical conformal mapping could transform the planar structure into cylindrical one which will not introduce geometrical singularities?...