Optical metasurfaces are an upcoming technological advancement beyond traditional diffractive optical devices, where the individual meta-atom can be engineered with flexibility and accuracy down to subwavelength scale. The wavefront manipulation using polished elements of wavelength scale can be replaced by metasurfaces that rely on artificial nanostructure-based electromagnetic excitation to engineer light properties of phase-amplitude and polarization with much better and more accurate control. Their compatibility with nano and micro-fabrication techniques and small form factors makes them suitable for integration with any nanotechnology-based platform, with scope for developing novel optical elements-based devices. For optical metasurfaces, the meta-atom dimensions scaled to small visible wavelengths pose a demanding accuracy for the fabrication of meta-atoms, with a growing need to find optimal solutions for improvement in yield and feasibility towards large-scale practical applications. In this dissertation, I have addressed this issue by using the gap-surface plasmon (GSP) based metasurfaces that support standing wave type resonances, which can scale the meta-atoms to larger sizes based on higher-order modes, without compensating much for the efficiency in engineering light. Furthermore, it provides unique features of dual-bandwidth control accessible by fundamental and third-order resonances for individual meta-atoms and subsequent improvement in the range of meta-atoms for engineering the devices. In addition, the metasurfaces that support standing wave resonances have top and bottom metal layers, which can freely accommodate different types of metals can subsequently improve the range of meta-atoms to the fullest.
I present this work by firstly, highlighting the historical development towards the strategy of metasurfaces and the principles of engineering light based on different types of metasurfaces. Then, I focus on the physical picture of GSP metasurfaces that can support fundamental and third-order resonances suitable for metasurface-based applications. The physical picture is also analysed with the study of binary combinations of three common plasmonic metals to accommodate top and bottom layers.
Lastly, I highlight the applications of beam steering and color printing applications based on the third-order periodic dimension of the metasurfaces, which have been designed, fabricated, and characterized to demonstrate the unique capabilities of using GSP-based metasurfaces as part of this work. The capabilities of better yield and dual-bandwidth features are demonstrated using beam steering application. While the improvement in the meta-atom range is demonstrated by color printing application through a wider range of colors based on both geometric parameters of dimension supporting the third-order GSP resonance and material parameters of different metal combinations.
© 2021 – Rucha Anil Deshpande
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