In this work we design and experimentally realize a photonic kagome metasurface exhibiting a Wannier-type higher-order topological phase. We demonstrate and visualize the emergence of a topological transition and opening of a Dirac cone by directly exciting the bulk modes of the HOTI metasurface via solid-state immersion spectroscopy. The open nature of the metasurface is then utilized to directly image topological boundary states. We show that, while the domain walls host 1D edge states, their bending induces 0D higher-order topological modes confined to the corners. The demonstrated metasurface hosting topological boundary modes of different dimensionality paves the way to a new generation of universal and resilient optical devices which can controllably scatter, trap and guide optical fields in a robust way.
In the recent decade two-dimensional transition metal dichalcogenides (2D TMDs) has attracted great attention in a variety of optoelectronic applications including photodetectors, optical chemical sensors, light-emitting diodes, lasers, and opto-valleytronic devises because of their high ON/OFF current ratios, low sub-threshold switching, strong photoluminescence, controllable valley polarization and high thermal stability. Despite their excellent optoelectronic properties, their optoelectronic applications are limited by the weak light-matter interaction in 2D TMDs due to the atomic thickness. Because plasmonic metal nanoparticles (NPs) have the capability to concentrate light beyond the diffraction limit, there is an emerging trend of exploiting light-matter interactions in hybrid systems consisting of 2D TMDs and plasmonic metal NPs for boosting the performance of 2D TMD-based optoelectronic devices. Plasmonic metal NPs have been employed to enhance light-matter interactions in quantum emitters including dye molecules and quantum dots through mechanisms such as Fano interference, strong coupling, plasmon-induced resonance energy transfer, and plasmon-enhanced emission. However the understanding and the active control of the interaction between 2D TMD and plasmonic NPs are still limited. So, herein, we report two tunable plasmon-exciton interactions that are novel in hybridized systems consist of 2D TMD and plasmonic NPs: (1) tunable plasmon-induced resonance energy transfer from a single Au nanotriangle (AuNT) to monolayer MoS2; (2) tunable Fano resonance and plasmon-exciton coupling in a single AuNT on monolayer WS2 at room temperature. In the first case, we report the first observation and tuning of plasmon-trion and plasmon-exciton resonance energy transfer (RET) from a single AuNT to monolayer MoS2 at room temperature. We achieved these phenomena by the combination of rational design of hybrid 2D TMD-plasmonic NP systems and single-nanoparticle measurements. By combining experimental measurements with theoretical calculations, we conclude that the efficient RET between SPs of metal NPs and excitons or trions in monolayer MoS2 is enabled by the large quantum confinement and reduced dielectric screening in monolayer MoS2. In the second case, we report tunable Fano resonances and plasmon-exciton coupling in 2D WS2-AuNT hybrids at room temperature. The tuning of Fano resonances and plasmon-exciton coupling was achieved by active control of the WS2 exciton binding energy and dipole-dipole interaction through controlling the dielectric constant of the surround medium. Specially, Fano resonances are controlled by the exciton binding energy or the localized surface plasmon resonance (LSPR) strength through tuning the dielectric constant of surrounding solvents or the dimension of AuNTs. Additionally, we observe a transition from weak to strong plasmon-exciton coupling when increasing the dielectric constant of surrounding solvents. Large coupling strength of 80-100 meV is obtained at room temperature due to the strong field localization of the AuNTs and large transition dipole moment of the WS2 exciton. Our results provide guidance on systematic tuning of the Fano line-shape and Rabi splitting energies at room temperature for 2D TMD-plasmonic NP hybrids.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.