Non-Hermitian and Topological Plasmonic Devices for Light Manipulation at the Nanoscale

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Title: Non-Hermitian and Topological Plasmonic Devices for Light Manipulation at the NanoscaleOptics and photonics play a vital role in both fundamental science and cutting-edge technologies. Examples include solar energy harvesting and conversion, fiber optic communications, and optical data storage, to name a few. New strategies are urgently needed to further advance the design and implementation of nanoscale photonic devices, in which the loss and defect impose significant limitations on the performance of the devices. The goal of this project is to investigate the novel phenomena and functions, such as unidirectional transport of light waves, defect-immune photonic states, and nanoscale lasers with low input power, by engineering the spatial distribution of material properties as well as the structural topology. The success of the project will lead to a crucial step towards the development of integrated photonic devices with low energy consumption, small footprint, and robust performance to benefit optical information processing, secure communications, enhanced sensing, and quantum technology for a wide range of applications. In addition, the project provides an interdisciplinary platform to engage students, especially those from underrepresented groups, and foster them to become next-generation scientists and engineers in the fields of photonics, materials science, nanotechnology and applied physics. The proposed research lies at the interface of nano plasmonics, non-Hermitian photonics, and topological optics. The interplays among the three rapidly growing fields have profound implications. On one hand, plasmonics has shown remarkable abilities to beat the diffraction limit, generate local hotspots with electric fields amplified by orders of magnitude, and significantly enhance light-matter interactions. However, it is known that the loss and imperfection in geometries strongly influence the optical responses of plasmonic nanostructures and the performance of plasmonic devices. The notion of non-Hermitian and topological physics can potentially address these challenges. On the other hand, up to date, non-Hermitian optics and topological photonics have been mostly realized in systems with the feature size at the micrometer scale. It is of great interest to investigate if and how the two concepts could enable novel properties and applications at the nanoscale. Plasmonics provides an excellent testbed in this regard, thanks to the large flexibility in engineering the geometry, resonance, coupling, dispersion, and complex dielectric constants of subwavelength plasmonic elements. The proposed project consists of three research thrusts, including (1) demonstration of unidirectional excitation and reflection of surface plasmon polaritons in non-Hermitian plasmonic devices by modulating the permittivity in the complex plane; (2) investigation of topological states in one-dimensional and two-dimensional non-Hermitian plasmonic structures, which are immune to defects, imperfections, and disorder; and (3) numerical and experimental study of low-threshold and topologically protected plasmonic nanolasers. The research findings of the project will open up a new route to efficiently generate, harness and transport light and energy in an unprecedented manner.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.