Multipolar Analysis of Structural Colour in Metasurfaces andHomogenisation in Metamaterials

Bhagowati, Sanskar (2025) Multipolar Analysis of Structural Colour in Metasurfaces andHomogenisation in Metamaterials. Masters thesis, Indian Institute of Science Education and Research Kolkata.

Text (MS Dissertation of Sanskar Bhagowati (20MS094)) 20MS094_Thesis_file.pdf - Submitted Version Restricted to Repository staff only Download (9MB)

Abstract

Metasurfaces and metamaterials have demonstrated immense potential in manipulating light-matter interactions. One promising avenue is structural colouration through metasurfaces, which offers a powerful approach for nanoscale colour control with applications in photonics, display technologies, and anti-counterfeiting. Metamaterials, likewise, open up exciting possibilities by enabling the engineering of materials with tailored electromagnetic responses, achievable through the development of advanced analytical tools in parallel. While structural colour has been successfully demonstrated using metasurfaces, analytical solutions for light scattering and colour mapping, particularly for studying metamerism, remain unexplored. Although previous studies have highlighted the functional advantages of structural colour, significant challenges persist in efficiently predicting colour outcomes and identifying metameric metasurfaces. Traditional numerical solvers are computationally expensive compared to semi-analytical methods. To overcome these challenges, this thesis presents a systematic investigation of metamerism. This approach identifies metameric pairs, structurally distinct designs that yield visually indistinguishable colours, demonstrating how structural parameters can be tuned to achieve desired colour appearances. Extending the effective T-matrix formalism from 2D to 3D, we further investigate the homogenization and retrieval of effective parameters in metamaterials by incorporating the Kramers-Kronig relations and calculating the effective refractive index from the extinction cross-section under single illumination. These findings underscore the versatility of the T-matrix approach for both metasurface design and metamaterial homogenization. The methodologies presented not only streamline the simulation of complex nanophotonic systems but also pave the way for new directions in structural colour engineering and advanced material discovery.

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