Computational studies of linear and non-linear optical properties of nano-Structured metamaterials

摘要

In this thesis, a comprehensive analytical and numerical study of optical non-linear effectsudin plasmonic metamaterials is presented. The new results reported and describedudin this work can potentially have a significant impact on our understanding of electromagneticudphenomena in artificial optical materials, and facilitate the design and fabricationudof new active optical devices with new or enhanced functionality. Equally important,udthese results could lead to deeper physical insights into the fundamental propertiesudof these metamaterials.udTo this end, a new analytical formalism based on the multiple scattering theoryudhas been developed, a theoretical framework that allows one to fully characterise theudlinear and non-linear electromagnetic properties of arbitrary distributions of metallicudnanowires. This formalism is unique in allowing readily retrieval of the spatial distributionudof the electromagnetic field both at the fundamental frequency (linear analysis)udand the second harmonic (non-linear optical response). The formalism also allows forudboth frequency- and time-domain investigations.udBased on this work, a new software tool with unique features has been implementedudand used to achieve a better understanding of the intricate electromagneticudphenomena occurring in nano-structured plasmonic systems. In particular, this tooludhas been used to design and investigate numerically several new non-linear plasmonicudstructures and nanodevices with remarkable properties. Amongst them were non-linearudplasmonic cavities with high quality factors, plasmonic cavities that support non-linearudwhispering gallery modes and sub-wavelength non-linear plasmonic sensors with enhancedudsensitivity and reduced device volume.udSeveral other plasmonic systems that show tremendous potential for the developmentudof advanced metamaterials-based devices have also been explored. Specifically, itudwas demonstrated that nano-patterned metasurfaces can be employed to achieve polarisationudcontrolled electromagnetic response in arrays of cruciform apertures and magnetisationudinduced second harmonic generation in chiralmetallic structures. The numericaludinvestigation of photonic superlattices exhibiting zero effective index of refractionudhas also been discussed.