Topological bound states in the continuum of plasmonic lattices

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• Grazia Salerno, Aalto University
• Thursday 04 May 2023, 13:15-14:30
• Theory Library.

If you have a question about this talk, please contact Dr Hannah Price.

Bound states in the continuum (BICs) are general solutions of wave equations that arise as topological defects protected by symmetries of the system. In photonics, BICs show a winding of the light polarization around a specific momentum, akin to a vortex with a non-trivial topological charge. These modes have infinite quality factors and no far-field radiation while carrying protected optical angular momentum, making them of interest for various applications in lasing and sensing. We study BICs in plasmonic lattices composed of complex unit cells containing multiple gold nanoparticles. The system is brought to the lasing regime by combining it with a dye molecule liquid acting as a gain medium. We show that these structures exhibit lasing emission with non-trivial polarization properties that are attributed to BICs. By combining group theory with a careful design of the lattice, we demonstrate that different BICs with distinct topological charges can lase in various regimes, while our simulations confirm that the modes’ quality factors undergo a loss-induced topological transition as the scale of the unit cell changes. Our results offer new insights into the physics of BICs and may open up opportunities for designing novel topological photonic devices.

This talk is part of the Theoretical Physics Seminars series.

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