Dissertations and Theses
Date of Award
2023
Document Type
Dissertation
Department
Engineering
First Advisor
Alexander Khanikaev
Keywords
topological photonics, photonic metamaterials, spectroscopy, nanostructures
Abstract
Topological phases in photonics attract a lot of attention due to their unique properties which allow controlling optical coupling and electromagnetic field distributions in nanostructures. Diverse phenomena supported by photonic topological structures include robust scatter-free waveguiding, an extreme confinement of light, lasing and strong coupling with novel low- dimensional materials. A very convenient integration with on-chip optical devices and also with quantum dots or monolayers of van der Waals materials promise even brighter future for photonic topological insulators as a useful platform for innovative photonic and compact quantum devices.
In the course of my dissertation work, I investigated topological structures with preserved time-reversal symmetry (non-magnetic materials) whose topological properties rely on lattice or sublattice symmetries. These structures were fabricated in a thin silicon slab and their design could be adjusted for operating in almost any optical frequency range, from visible to mid-infrared. One type of topological insulators which we studied is Wannier type higher-order topological system implemented in a breathing kagome lattice. In this platform we were able to visualize higher-order topological states, confined in 1D (edge states) and even 0D (corner states), at optical frequencies. These states are potentially interesting for applications such as trapping of light or lasing via integration with active materials, e.g., perovskite nanocrystals, which we also demonstrated in our recent works. To study topological states which reside under the light cone I applied different experimental techniques, including a dark field microscopy for visualization of modes in the far- field, angle-resolved solid immersion spectroscopy, which allowed to reveal a bulk band structure and also near-field imaging with a scattering type scanning near-field optical microscope to directly observe higher order topological states.
In contrast to valley-Hall topological structures that operate below the light line, spin-Hall topological photonic crystals offer the possibility to probe spin-polarized boundary states above the light line at nearly normal incidence via far-field illumination. We studied spin-Hall topological phase based on breathing honeycomb lattice and proposed a new approach to control properties of topological boundary states via engineering the interface profile between topological and trivial domains. The proposed adiabatic domain wall supports the modes with improved bandgap crossing behavior, longer radiative lifetimes and propagation distances, while retaining their topological resilience.
Trapped modes with distinct radiation profiles were demonstrated in our work where we created a cavity with spatially inhomogeneous mass term based on photonic spin-Hall topological design. Realization of Dirac-like dispersion in photonic structure allowed relativistic-like spin- degenerate trapping of light. Coupling of the cavity to spin-polarized edge states confirmed spin- selective directional excitation of the cavity modes. Our convincing results showed that spin-full metasurfaces with Dirac dispersion can potentially serve as a source of arbitrary vector beams for on-chip generation of structured light.
Recommended Citation
Vakulenko, Anton, "Design and experimental observation of topological states in photonic metasurfaces" (2023). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/1135