Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 36: Poster III

HL 36.1: Poster

Wednesday, March 20, 2024, 18:00–20:30, Poster E

Entangled two-photon absorption in 2D semiconductors — •Till Weickhardt and Giancarlo Soavi — Institute of Solid State Physics, Jena, Germany

The excitonic states in TMDCs lead to resonant enhancement of SHG and two-photon absorption (TPA) with huge cross-sections and have been proposed as gates for valleytronics.[1] To generate detectable populations of excitons in two photon processes with classical light and not damaging the monolayer it is necessary to use a pulsed laser with a broad spectrum. This limits the energy resolution of any experiment. In this work, we propose a possible way to remedy this problem by using energy-time entangled photons from spontaneous parametric down conversion (SPDC). This way, the photons are temporally synchronized in pairs and sum up to a precise and narrow energy spectrum while the distribution of single-photon energies can be broad.[2] This leads to higher efficiencies for TPA combined with spectral resolution beyond the Fourier limit. Entangled two-photon absorption (ETPA) has been demonstrated in fluorophores but never in solid-state systems.[3] To achieve this, two experimental requirements must be met: (i) a tunable narrowband laser to precisely hit the excitonic resonances of the TMDC under investigation. (ii) a SPDC source with high photon-pair flux, leading to an average power of at least 100 nW. While these requirements have already been met in our labs, first measurements of ETPA in TMDCs are still pending at this stage.

References: [1]Herrmann et al., Small 19, 2301126(2023) [2]Dayan et al., PRL 94, 043602(2015) [3]Tabakaev et al., PRA 103, 033701(2021)

Keywords: TMDC; exciton; valleytronics; quantum optics; nonlinear optics