The mid-infrared spectrum is a technologically important spectral range used for identifying molecular fingerprints in biology and chemistry, atmospheric transparent windows for free-space communications, and thermal-related events. The proposed research consists of establishing non-trivial topological (or surface-related) phenomena in collective plasmon-polaritonic excitations. This will then create a platform for novel nanophotonic components (waveguides, splitters, and others) which can support non-reciprocal and ideally unidirectional wave-propagation in the mid-infrared frequency. So far, all designs of photonic topological insulators involve bulk ferromagnetic materials, metals and dielectrics. The characteristics of these metamaterials are predefined by design and non-tunable. Our approach is to utilize electrically tunable quantum materials and their plasmon-polaritonic modes. For example, the directionality of the non-reciprocal plasmon-polaritons mode can be electrically controlled on-the-fly. If successful, this research would deliver integrated mid-infrared nanophotonics solutions, such as optical modulators, isolators and routers, on-chip mid-infrared lasers, and on-chip sensing of chiral biomolecules. On enhancing both education and outreach, this project will implement a three-pronged broadening participation program. First, it will employ a unified plan of action for the participating PIs to incorporate quantum materials nanophotonics into current undergraduate curricula, including classes in quantum materials, photonics, spectroscopy and processing. Secondly, the research team will organize and establish a summer experience workshop for K-12 students in the local communities. Third, the team will organize summer school and additional scientific workshops on quantum materials nanophotonics. These activities will be closely coordinated with the institution and reported to NSF annually.
Non-trivial Berry phase in its ground state electronic wavefunction has recently inspired its experimental observation in 2D materials, such as valley Hall transport and circular dichroism in gapped Dirac materials. However, it was predicted that the underlying Berry phase of the electronic ground state should also imbue the collective electronic excitations with a completely new non-reciprocal character known as Berry plasmons. This project will investigate two fundamental questions: 1) How are the collective modes, including plasmons-polaritons of topological materials, impacted by the non-trivial topology of their single-particle electronic states? 2) How can we harness topological plasmons for creating new optoelectronic devices? To answer these questions, we propose a joint theoretical and experimental program, with the following goals; perform proof-of-principle experiments to verify the predicted collective excitation, Berry plasmons, and demonstrate a suite of mid-infrared nanophotonics components such as energy efficient non-reciprocal optical modulators and routers, on-chip mid-infrared pump and probe lasers, and integrated platform for sensing of chiral biomolecules. The program integrates condensed matter physics, materials and electromagnetics modeling, advanced inverse photonic system design, state-of-the-art 2D materials device fabrication, advanced hyperspectral imaging with near field infrared techniques, and mid-infrared integrated photonics components. This 4 years program involves University of Minnesota, Columbia University, Stanford University and University of Pennsylvania.
