Dielectric Superlattice Nanostructures for Metasurfaces and Optoelectronics

Advances in nanoscale photonics have revealed powerful routes for shaping electromagnetic fields; yet, two persistent challenges continue to limit the performance of compact optical systems: achieving high-fidelity wavefront control in the visible range without sampling artefacts, and expanding the momentum space accessible to polaritonic modes in naturally anisotropic materials. Both limitations stem from the same underlying constraint: the discrete or intrinsic structure of the optical environment restricts how light can accumulate phase, amplitude, and momentum. This thesis explores how carefully engineered geometry and dielectric structuring can overcome these restrictions and provide deterministic control over both propagating and strongly confined optical fields. To address the limitations of discretized metasurface phase profiles, this work develops a continuous and finely sampled TiO₂ meta-optic platform that enables high-numerical-aperture metalenses to operate near the diffraction limit. A hybrid unit-cell/supercell design strategy minimizes undersampling artefacts and ensures accurate realization of the ideal phase distribution. Experimental characterization confirms the creation of bright, symmetric focal spots whose dimensions closely match theoretical predictions, demonstrating that deterministic geometric design can deliver high-efficiency wavefront shaping in the visible regime. The same geometric philosophy is extended toward full complex-amplitude control through analytically designed metasurface holography. By encoding phase and amplitude via controlled displacement and scaling of meta-atoms, the method adheres exactly to Fresnel propagation without requiring iterative optimization. Simulations and preliminary measurements demonstrate accurate image reconstruction with reduced speckle and enhanced fidelity compared to conventional phase-only holograms. Beyond propagating fields, the thesis examines how artificial dielectric environments can influence the dispersion and confinement of polaritonic excitations, thereby unlocking higher-momentum optical states. Engineered alternating dielectric oxide layers, such as Al₂O₃/HfO₂ nanolaminate substrates, are shown to possess effective permittivities unattainable in bulk materials, enabling stronger hybridization with phonon-polaritons in 2D materials, such as hexagonal boron nitride (hBN). This tailored hybrid environment supports enhanced confinement, modified modal dispersion, and access to momentum regimes beyond the natural limits of the constituent materials. Together, these results show how deterministic control of phase, amplitude, and modal dispersion can be achieved through distinct but complementary nanoscale strategies. The metasurface metalenses and holographic platforms demonstrate how geometric design enables accurate manipulation of propagating optical wavefronts in the visible regime, while the nanolaminate-2D material system reveals how engineered dielectric environments can reshape polaritonic modes and push light-matter interactions into previously inaccessible momentum ranges. Although these systems operate in different spectral domains and target different physical regimes, they collectively illustrate the broader principle that carefully tailored nanoscale structuring, whether geometric or dielectric, provides a powerful route for expanding and refining the optical functionalities achievable in compact photonic platforms.