Excitons in atomically thin semiconductors are sensitive to their electronic and photonic environments.
Therefore, they exhibit rich exciton dynamics. They are confined in the vertical direction while extending
and diffusing along the atomically thin plane. Excitons can also interact with each other, notably to reduce
light emission at high densities through exciton-exciton annihilation. Furthermore, their fluorescence is
affected by their nanoscopic environment. Here we present our experimental and theoretical results on
the fluctuation, diffusion, and annihilation of excitons near nanostructures. Our results have implications
for exciton-based sensors, single-photon sources based on 2D materials, and efficient and high-power
light-emitting devices.
This Conference Presentation, “Nanophotonic chirality transfer to dielectric Mie resonators,” was recorded for Photonics Europe 2022, in Strasbourg, France.
We demonstrate the strong coupling between excitons in organic molecules and all-dielectric metasurfaces supporting Mie surface lattice resonances (MSLRs). MSLRs have extended mode volumes and large quality factors, which enables to achieve collective strong coupling with large coupling strengths and Rabi energies. Moreover, due to the electric and magnetic character of the MSLR given by the Mie resonance, we show that the hybridization of the exciton with the MSLR results in exciton-polaritons that inherit this character as well. Our results demonstrate the potential of all-dielectric metasurfaces as novel platform to investigate and manipulate exciton-polaritons in low-loss polaritonic devices.
The interaction of circularly polarized light with matter is the basis for molecular circular dichroism spectroscopy, optical spin manipulation, and optical torques. However, chiroptical effects are usually hampered by weak chiral light-matter interaction. Nanophotonic structures can enhance optical intensity to boost interactions, but magnifying chiral effects requires that the near field remains chiral in the process.
Here, we propose the conditions, limits and guidelines for enhancing different chiroptical effects near achiral metasurfaces with maximum chirality of the evanescent fields. We illustrate these conditions with arrays of metal and dielectric nanodisks and decompose their distinct electromagnetic metrics into propagating and evanescent Fourier orders. We prove that chirality metrics like circular dichroism and the degree of circular polarization, which go hand-in-hand in the far field for propagating plane waves, are incompatible in the evanescent near field. As a result, a nanostructure cannot be universally optimal for different chirality metrics and therefore applications. For example, arrays tailored for enhanced spin excitation with spatially uniform circular polarization destroy circular dichroism. Conversely, we predict a limit of maximum attainable circular dichroism in highly evanescent Fourier orders through a simple relation with the evanescent wavevector and polarization. We demonstrate that silicon nanodisk arrays can enhance chiral effects within these constraints.
Our results define the limits on the ability of nanophotonic platforms to enhance different chiral light-matter interactions simultaneously. Our work provides design rules for diverse chiroptical applications such as molecular spectroscopy, information technology and optical nanomanipulation.
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