Floquet Topological Photonic Insulators Based on Coupled Microring Lattices

• Author / Creator

  Afzal, Shirin

• Topological photonic insulators (TPIs), a new phase of matter in photonics, have attracted considerable attention due to their unique ability to transport light via topologically-protected edge states that are immune to defect scattering. Among the various potential applications, this property can be exploited to engineer robust photonic devices that are insensitive to fabrication imperfections. In this thesis, we explored the physics and applications of a class of topological photonic insulators, known as Floquet insulators, which are based on periodically-driven quantum systems. In particular, we proposed a new Floquet topological photonic system based on two-dimensional (2D) lattices of coupled microring resonators. We first developed a mathematical formulation for a general 2D microring lattice as a periodically-driven system and derived its Floquet-Bloch Hamiltonian, which allowed us to characterize and study the topological properties of the lattice. We showed that our lattice can be designed to exhibit a wide range of topological behaviors, including normal insulator, Chern insulator, and anomalous Floquet insulator. To validate our theoretical results, we realized Floquet topological photonic insulators based on 2D lattices of coupled octagon resonators in the Silicon-on-Insulator (SOI) platform and experimentally verified their nontrivial behaviors through the observation of topologically protected edge modes. Notably, our Floquet microring lattice is the first realization of an AFI on a nanophotonic platform. Our proposed microring lattice thus provides a versatile nanophotonic platform for investigating Floquet TPIs and exploring their applications.
  We also proposed and experimentally demonstrated a new mechanism for achieving high quality factor resonances in a Floquet TPI. The new resonance effect, which we call Floquet Defect mode resonance (FDMR), is achieved by perturbing the driving sequence of the system to isolate and tune the phase of a Floquet bulk mode to induce constructive self-interference. The FDMR can be regarded as a Floquet counterpart of defect-mode resonance in static, undriven systems, except that here the perturbation is drive-dependent and varies periodically along the path of system evolution. Notably, the FDMR is cavity-less, i.e., it does not require physical boundaries; instead, its spatial localization pattern is dictated by the driving sequence of the Floquet system and is distinctly different for topologically trivial and nontrivial lattices. Due to the lack of interface scattering, FDMRs can potentially have very high quality factors. We experimentally demonstrated FDMRs in Floquet microring lattices in SOI, achieving the highest quality factor reported to date for 2D topological photonic resonators. We envision FDMR to have a wide range of applications in topological photonics, including lasers, filters, sensors, and applications in nonlinear and quantum cavity optics.

• Subjects / Keywords

  • Floquet Topological Photonic Insulators
  • Floquet Defect Mode Resonance
  • Microring resonators
  • Silicon Photonics

• Graduation date

  Fall 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-j5hx-2z28

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.