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Disentangling the Temporal Dynamics of Nonthermal Electrons in Photoexcited Gold Nanostructures
Author(s) -
O'Keeffe Patrick,
Catone Daniele,
Di Mario Lorenzo,
Toschi Francesco,
Magnozzi Michele,
Bisio Francesco,
Alabastri Alessandro,
Proietti Zaccaria Remo,
Toma Andrea,
Della Valle Giuseppe,
Paladini Alessandra
Publication year - 2021
Publication title -
laser and photonics reviews
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.778
H-Index - 116
eISSN - 1863-8899
pISSN - 1863-8880
DOI - 10.1002/lpor.202100017
Subject(s) - femtosecond , photoexcitation , ultrashort pulse , ultrafast laser spectroscopy , electron , plasmon , thermalisation , spectroscopy , materials science , physics , photodetection , optoelectronics , atomic physics , laser , optics , excited state , quantum mechanics , photodetector
The study of nonthermal electrons, generated upon photoexcitation of plasmonic nanostructures, plays a key role in a variety of contexts, from photocatalysis and energy conversion to photodetection and nonlinear optics. Their ultrafast relaxation and subsequent release of energy to a low energy distribution of thermalized hot electrons has been the subject of a myriad of papers, mostly based on femtosecond transient absorption spectroscopy (FTAS). However, the FTAS signal stems from a complex interplay of different contributions arising from both nonthermal and thermal electrons, making the disentanglement of the two a very challenging task, so far accomplished only in terms of numerical simulations. Here a combined approach is introduced, based on a post‐processing of the FTAS measurements guided by a reduced semiclassical model, the so‐called extended two‐temperature model, which has allowed the purely nonthermal contribution to the pump‐probe experimental map recorded for 2D arrays of gold nanoellipsoids to be isolated. This approach displays the intimate correlation between electron energy and probe photon energy on the ultrafast time‐scale of electron thermalization. It also sheds new light on the ultrafast transient optical response of gold nanostructures, and will help the development of optimized plasmonic configurations for nonthermal electrons generation and harvesting.