MODELING, DESIGN AND APPLICATIONS OF OPTICAL METASURFACES

Abstract

Metasurfaces, ultrathin arrays of engineered subwavelength resonators, have emerged as powerful platforms for precise control of light, enabling compact and multifunctional devices for imaging, sensing, communication, and secure information processing. This thesis, “Modeling, Design and Applications of Optical Metasurfaces”, advances the field through systematic exploration of achiral and chiral architectures, moving from fundamental design principles to multifunctional applications, and from reflection-based to transmission-based operation. The work begins with achiral metasurfaces, where a dielectric metalens inspired by the human eye is developed using concentric cylindrical resonators. The design reduces the aspect ratio of the meta-atoms, ensuring enhanced structural robustness and fabrication feasibility. Attention then shifts to chiral metasurfaces under oblique incidence, where multilayer and perovskite- based structures achieve strong circular and linear dichroism, including triple-band responses for biosensing applications such as hemoglobin, glucose, and cancer cell detection. To overcome the limitations of oblique excitation, intrinsic chirality under normal incidence is realized using semi-circular ring arrays, producing near-perfect absorption with high circular dichroism across telecommunication bands. These structures also enable secure image encryption, demonstrating potential in optical communication and information security. VISHAKHA SHARMA vii Building further, reflective and transmissive chiral metasurfaces are developed for multifunctional control. A spin-multiplexed reflective metalens achieves polarization-selective focusing, while an all-dielectric meta-coded firewall with graphene tunability enables polarization-gated transmission for secure authentication and friend-or-foe recognition. In conclusion, the thesis establishes a coherent progression from achiral to advanced chiral metasurfaces, integrating concepts of absorption, dichroism, multiplexing, and tunability. The results highlight metasurfaces as versatile and scalable platforms for next-generation technologies spanning communication, defense, biomedical diagnostics, and photonic encryption.