Armando Genco (Politecnico di Milano)
Ultrafast dynamics of coherent exciton-polaritons in van der Waals semiconductor metasurfaces
Abstract – Metasurfaces based on transition metal dichalcogenides (TMDs) have emerged as a promising platform for controlling light at the nanoscale due to their exceptional optical properties, including strong excitonic responses and intrinsically high refractive index. Unlike traditional dielectric metasurfaces, TMD-based platforms enable highly confined optical modes with minimal losses, making them ideal for applications in nanophotonics. The high refractive index of TMDs plays a crucial role in supporting Mie-type resonances and facilitating the realization of bound states in the continuum (BICs), which exhibit theoretically infinite quality factors and extreme field localization. The interplay between BICs and TMD metasurfaces opens new avenues for enhancing light-matter interactions, paving the way for efficient nonlinear optics, lasing, and quantum photonic devices.
In my talk, I will discuss highly tunable optical metasurfaces composed of nanorod-type unit cells made of bulk WS2, where excitons are strongly coupled to quasi-BIC modes forming polariton states at room temperature. I will first focus on the often-overlooked polarization-dependent angular dispersion of the resonant modes, which we characterized across the entire momentum space using hyperspectral imaging. The photonic band structure plays a crucial role in shaping the nonlinear behavior and ultrafast dynamics of polaritons, which we investigated through various pump-probe spectroscopy techniques. Leveraging high temporal resolution, we tracked the coherence of strong light–matter coupling, revealing pronounced oscillations in the pump-probe traces, signature of polariton quantum beats.”
Bio – Dr. Armando Genco is an Assistant Professor at Politecnico di Milano (Italy) and an expert in optics and photonics. His research primarily explores light-matter interactions between excitons in quantum materials and photons confined in optical micro- and nanoresonators, both in static and transient conditions.
This is an in-person seminar. If you opt to join via zoom use meeting ID 880 6343 0208 Passcode 553685