Competing Auger-Like and Intraband Excitations Drive Anomalous Modulations in Indium Tin Oxide
Abstract
Transparent conducting oxides near their epsilon-near-zero frequency exhibit near-unity ultrafast modulations of the refractive index which have enabled the field of time-varying metamaterials, yet the underlying carrier dynamics at high driving fluences remain poorly understood. Here, we report ultrafast modulations in the reflectivity and transmissivity of indium tin oxide, and a non-monotonic oscillatory behavior. This is especially evident in the time evolution of the complex Fresnel coefficients retrieved directly from pump-probe spectrograms using an optical gating technique, GRUMPY FROG. The dynamics of the retrieved plasma frequency and damping coefficient are well captured by an extended two-temperature model incorporating a competing nonlinear interband process: at high fluences, Auger-type scattering of hot conduction electrons promotes valence band carriers, increasing the plasma frequency while accelerating hot-electron cooling and raising the damping coefficient. These results clarify the origin of anomalous high-fluence dynamics in indium tin oxide and identify a fluence-tuneable modulation dynamic with direct implications for ultrafast refractive index engineering in time-varying photonic devices and optical switching.
Versions
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BibTeX
@misc{harwood2026competing,
title = {{Competing Auger-Like and Intraband Excitations Drive Anomalous Modulations in Indium Tin Oxide}},
author = {Anthony C Harwood and Sean Z J Lim and T V Raziman and Yan Li and Joseph Stones and John W G Tisch and Simon A R Horsley and Stefano Vezzoli and John B Pendry and Riccardo Sapienza},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2605.21432},
eprint = {2605.21432},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2605.21432},
}
RIS
TY - UNPB
TI - Competing Auger-Like and Intraband Excitations Drive Anomalous Modulations in Indium Tin Oxide
AU - Anthony C Harwood
AU - Sean Z J Lim
AU - T V Raziman
AU - Yan Li
AU - Joseph Stones
AU - John W G Tisch
AU - Simon A R Horsley
AU - Stefano Vezzoli
AU - John B Pendry
AU - Riccardo Sapienza
PY - 2026
DA - 2026/08/26
PB - arXiv
DO - 10.48550/arxiv.2605.21432
UR - https://arxiv.org/abs/2605.21432
AB - Transparent conducting oxides near their epsilon-near-zero frequency exhibit near-unity ultrafast modulations of the refractive index which have enabled the field of time-varying metamaterials, yet the underlying carrier dynamics at high driving fluences remain poorly understood. Here, we report ultrafast modulations in the reflectivity and transmissivity of indium tin oxide, and a non-monotonic oscillatory behavior. This is especially evident in the time evolution of the complex Fresnel coefficients retrieved directly from pump-probe spectrograms using an optical gating technique, GRUMPY FROG. The dynamics of the retrieved plasma frequency and damping coefficient are well captured by an extended two-temperature model incorporating a competing nonlinear interband process: at high fluences, Auger-type scattering of hot conduction electrons promotes valence band carriers, increasing the plasma frequency while accelerating hot-electron cooling and raising the damping coefficient. These results clarify the origin of anomalous high-fluence dynamics in indium tin oxide and identify a fluence-tuneable modulation dynamic with direct implications for ultrafast refractive index engineering in time-varying photonic devices and optical switching.
ER -