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Speaker: Alessandra Di Gaspare - Cnr Nano
Title: Terahertz optical nonlinearities in Dirac matter: mending the 24-60 micron gap in the far infrared range
Abstract
Photonic technologies that exploit nonlinearities in material systems offer groundbreaking opportunities for the development of compact and cost-effective active optoelectronic devices. The unique combination of strong field confinement and giant, tunable optical nonlinearities provided by nanostructured Dirac materials has enabled the demonstration of harmonic generation in the elusive far-infrared spectral range (5–12 THz), which overlaps with the Reststrahlen band of III–V crystals, the foundational materials of solid-state light emitters.
In this talk, we present the first demonstration of frequency up-conversion in the 6–10 THz range in electrically-pumped microlasers through the integration of various Dirac-material-based metamaterials. By exploiting the nonlinear susceptibilities of these composite structures, and through a combination of electrical gating and material engineering in either ordered graphene multistacks or tailored topological insulators, we demonstrate the controlled generation of second- and third-harmonic signals with microwatt-level output powers. These results pave the way for a new and versatile platform for compact, tunable sources of coherent radiation across a frequency range that has so far remained inaccessible to solid-state lasers.
[1] A. Di Gaspare et al., Compact terahertz harmonic generation in the Reststrahlenband using a graphene-embedded metallic split ring resonator array. Nat. Commun., 15 (1), 2312 (2024)
[2] A. Di Gaspare et al., Electrically driven heterostructured far-infrared wire lasers with integrated graphene plasmons. Nat. Nanotechnol., 20 (11), 1611–1617 (2025)
[3] A. Di Gaspare et al., Second and third harmonic generation in topological insulator-based van der Waals metamaterials. Light Sci Appl 14, 337 (2025)
The Seminar is realized in the framework of the funded projects
UE H2020-FETOPEN-2018-2020 - Open project EXTREME IR. GA nr 944735
European Research Council through the ERC project NODE and EPSRC (UK) programme grants ‘TeraCom’ (EP/W028921/1).)
NAME (EP/V001914/1).
Host: Pisa Nano Colloquia Committee