Abstract

We investigate resonant third-harmonic generation in near-zero index thin films driven out-of-equilibrium by intense optical excitation. Adopting the Landau weak coupling formalism to incorporate electron–electron and electron–phonon scattering processes, we derive a novel set of hydrodynamic equations accounting for collision-driven nonlinear dynamics in sodium. By perturbatively solving hydrodynamic equations, we model third-harmonic generation by a thin sodium film, finding that such a nonlinear process is resonant at the near-zero index resonance of the third-harmonic signal. Thanks to the reduced absorption of sodium, we observe that third-harmonic resonance can be tuned by the impinging pump radiation angle, efficiently modulating the third-harmonic generation process. Furthermore, owing to the metallic sodium response at the pump optical wavelength, we find that the third-harmonic conversion efficiency is maximised at a peculiar thin film thickness where evanescent back-reflection provides increased field intensity within the thin film. Our results are relevant for the development of future ultraviolet light sources, with potential impact for innovative integrated spectroscopy schemes.

Details

Title
Resonant third-harmonic generation driven by out-of-equilibrium electron dynamics in sodium-based near-zero index thin films
Author
Silvestri, Matteo 1 ; Sahoo, Ambaresh 1 ; Assogna, Luca 1 ; Benassi, Paola 2 ; Ferrante, Carino 3 ; Ciattoni, Alessandro 3 ; Marini, Andrea 2 

 Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio, 67100 L’Aquila, Italy 
 Department of Physical and Chemical Sciences, University of L’Aquila, Via Vetoio, 67100 L’Aquila, Italy; CNR-SPIN, c/o Dipartimento to di Scienze Fisiche e Chimiche, Via Vetoio, Coppito, L’Aquila 67100, Italy 
 CNR-SPIN, c/o Dipartimento to di Scienze Fisiche e Chimiche, Via Vetoio, Coppito, L’Aquila 67100, Italy 
Pages
2003-2013
Publication year
2024
Publication date
2024
Publisher
Walter de Gruyter GmbH
ISSN
21928606
e-ISSN
21928614
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
3053956087
Copyright
© 2024. This work is published under http://creativecommons.org/licenses/by/4.0 (the “License”). Notwithstanding the ProQuest Terms and Conditions, you may use this content in accordance with the terms of the License.