EAGER: Engineering light-matter interaction via topological phase transitions in photonic heterostructures with aperiodic order

Trustees Of Boston University, Boston

Investigators

Abstract

Nontechnical description: Enhancing light-matter interaction processes such as the emission and absorption of photons using engineered optical nanostructures is a key feature to sustain the continuing development of a number of active devices that include light sources, modulators and optical sensors. These devices are the cornerstones of our present information age, where highly integrated semiconductor chips deliver and manipulate optical and electrical signals at ever increasing rates, directly or indirectly affecting every aspect of our society. In this project we propose a novel approach to boost light-matter interaction and tailor the fundamental transport processes that govern the photon dynamics in optical nanostructures. In particular we plan to engineer light-emitting photonic nanostructures with unprecedented optical properties by leveraging the interdisciplinary physics of the recently discovered topological phases in electronic systems. An example of such fascinating structures is provided by topological insulators, which are materials that behave as electrical insulators in their interior but can robustly conduct electricity on their surface irrespectively of perturbations and disorder. Our project explores photonic analogues of such systems extended to non-periodic geometries that support localized field solutions with greatly enhanced light-matter coupling and give rise to novel photon transport properties. The successful development of our research program may lead to a number of breakthroughs in the technologically strategic area of active silicon photonics, potentially resulting in transformative device applications to optical signal generation, propagation, processing and energy harvesting on the cost-effective silicon chip. The science of this project also offers exciting opportunities for the development of a vibrant educational and outreach plan on undergraduate and graduate levels. Technical description: Our proposal combines interdisciplinary perspectives on topological theory of deterministic aperiodic systems, device-level electromagnetic modeling of complex photonic structures, materials and device fabrication with spectroscopic characterization of light-emitting nanostructures based on silicon technology. The proposal builds on recent theoretical advancements that established a surprising connection between the rich physics of two-dimensional topological insulators and one-dimensional photonic quasi-crystals. In the project we will extend this vision to more general aperiodic systems and we will engineer topological phase transitions by smoothly connecting active waveguide structures with inequivalent topologies. Such devices will be fabricated using the widespread silicon technology that guarantees high-volume and low-cost production. Our goals will be achieved by first fabricating low-loss silicon compatible materials, such as transparent conductive oxides and nitrides doped with light emitting rare earth ions and Si quantum dots. We will then fabricate sub-wavelength slot waveguide gratings structures with aperiodic refractive index modulations that will controllably implement different types of topological transitions. The theoretical foundation to understand optical waves in such graded aperiodic systems will be developed in close partnership with experimental characterization of materials and devices. In particular, rigorous electromagnetic theory of and device-level modeling of the fabricated structures will be performed. The optical emission and transport properties of fabricated samples will be investigated by steady-state and time-resolved fluorescence spectroscopy in combination with structural characterization of materials. The proposed work paves the way to a novel class of photonic materials that leverage topological effects and aperiodic order to manipulate photon transport and light localization phenomena in active nanostructures. Moreover, this research can result in the discovery of novel surface phenomena in nanophotonics and will enable the development of new strategies to boost light-matter interaction in aperiodic systems with emission characteristics intrinsically determined by the nature of their topological invariants.