Disentangling the Ultrafast Nonlinear Optical Behavior of Plasmonic Resonances Near the Interband Transition. Issue 1 (17th August 2022)

• Record Type: Journal Article
• Authors: Schirato, Andrea; Silva, Mychel G.; Teles-Ferreira, Danielle C.; Manzoni, Cristian; de Paula, Ana Maria; Cerullo, Giulio; Della Valle, Giuseppe; Di Vece, Marcel
• Is Part Of: Advanced photonics research. Volume 4:Issue 1(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-08-17
• Subjects: nonlinear plasmonics -- plasmonic nanoparticles -- ultrafast spectroscopy; Photonics -- Periodicals; 621.36505
• DOI: 10.1002/adpr.202200081
• Languages: English
• ISSNs: 2699-9293

Abstract

Abstract : The photoexcitation of plasmonic nanostructures with ultrashort laser pulses allows for elucidating the mechanisms underlying the ultrafast nonlinear optical response of such systems, gaining insight into the fundamental processes triggered by light absorption at the nanoscale. To date, the complex temporal and spectral features of the photoinduced response are not fully understood, especially when the photon energies are close to the interband transitions of the metallic medium. Herein, the effects of photoexcitation of plasmonic nanostructures are studied by resorting to a combinaion of broadband transient absorption spectroscopy and semiclassical nonlinear simulations of the energy relaxation processes following illumination. The proposed approach enables an in‐depth disentanglement of all the contributions to the ultrafast transient optical response of supported gold nanocrystals. From these methods, the apparent transient blue shift of the localized plasmon resonance observed in the pump–probe signals is rationalized as an interplay between different and spectrally dispersed permittivity modulations, instead of a simple negative permittivity change, as it could be concluded based on the Fröhlich condition. The results provide a comprehensive understanding of the thermo‐modulational nonlinearities of plasmonic nanostructures exhibiting resonances close to the interband transition threshold. Abstract : A detailed analysis of the ultrafast nonlinear optical response of highly crystalline gold nanoparticles featuring plasmon energy close to metal interband transitions is reported. A combination of transient absorption spectroscopy and semiclassical modeling of the energy relaxation processes following photoexcitation enables to disentangle the mechanisms underlying the optical modulation and elucidate the origin of the experimental signal spectral shape.