Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 22: Focus Session: Young Semiconductor Forum

HL 22.8: Poster

Tuesday, March 19, 2024, 11:00–15:30, Poster F

Guided light in Angstrom thin samples - 2D van der Waals materials as a platform for novel optical devices and fundamental research — •Patryk Kusch, Mira Kreßler, and Stephanie Reich — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

Van der Waals materials, like graphene and transition metal dichalcogenides (TMDCs), offer exciting physical properties to explore such as high charge mobility, mechanical strength, and strong light emission. Particularly, monolayers of TMDCs are direct semiconductors that exhibit strong optical absorption by tightly bound excitons, quasiparticles formed by a bound state of an electron, and a hole within one monolayer. The binding energy is often so strong (several 100 meV) that they can be excited under ambient conditions. Furthermore, TMDCs promote the waveguiding of light. As we showed waveguided modes can propagate over several tens of micrometers through a 60 nm thin slab of MoS₂, which is interesting for the realization of novel optical devices. Here we demonstrate that light can be guided in Ångstrom thin WS₂ by imaging waveguided modes in real space with the scattering type scanning near-field optical microscope. The guided light couples with excitons, leading to the formation of exciton-polaritons, quasi-particles that are currently the focus of many scientific studies. We get access to their dispersion relation by taking nanoimages of the propagating polaritons at different excitation energies around the A and B exciton. It impressively shows that the coupling strength between guided light and excitons is in the strong coupling regime.

Keywords: Exciton-polariton; monolayer transition metal dichalcogenides; visible s-SNOM; nanoimaging; light-matter interaction