DFT modelling of fused silica electronic structure under strong laser-induced excitation

Arshak A. Tsaturyan; Elena Silaeva; Razvan Stoian; Jean-Philippe Colombier

doi:10.1117/12.2620774

3 June 2022 DFT modelling of fused silica electronic structure under strong laser-induced excitation

Arshak A. Tsaturyan, Elena Silaeva, Razvan Stoian, Jean-Philippe Colombier

Proceedings Volume PC12132, Advances in Ultrafast Condensed Phase Physics III; PC1213201 (2022) https://doi.org/10.1117/12.2620774
Event: SPIE Photonics Europe, 2022, Strasbourg, France

Abstract

Fused silica is an indispensable material in emergent photonic applications due to its unique optical, mechanical, and thermal properties, especially when it is nano-structured by an ultrashort laser pulse. The precision of the laser-induced modifications relies heavily on the control of the electron excitations and transient optical properties during the laser pulse. In this work we explored the evolution of fused silica bandgap at high densities of excited electrons, using Finite-Temperature Fractional Occupation Density Functional Theory (FT-DFT). Using a molecular-level approach, a molecular cluster based on (SiO4)4- tetrahedra was shown to reproduce accurately the physical properties of amorphous silica. The proposed theoretical approach (FT-DFT) correctly describes electronic and spatial structure both at the ground state and photoexcitation-induced thermalized hot states. Under electron-matrix nonequilibrium conditions, a bandgap narrowing by 2 eV and more is shown. This is explained by a pure geometry relaxation driven by the electron redistribution during the strong laser-induced excitation. The reason for the bandgap decrease is atomic rearrangement resulting in weakening of the bonds. Such behaviour of the system under excitation has a significative impact on its stability even if changes in geometry are limited to 7.5% bond elongation before the loss of integrity of the system. According to experimental data this atomic rearrangement can be expected on the femtosecond timescale. Defect formation in fused silica due to bond breaking is finally expected to occur for electronic temperatures above 2.8 eV.

Conference Presentation

Citation Download Citation

Arshak A. Tsaturyan, Elena Silaeva, Razvan Stoian, and Jean-Philippe Colombier "DFT modelling of fused silica electronic structure under strong laser-induced excitation", Proc. SPIE PC12132, Advances in Ultrafast Condensed Phase Physics III, PC1213201 (3 June 2022); https://doi.org/10.1117/12.2620774

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KEYWORDS

Silica

Modeling

Tellurium

Chemical species

Femtosecond phenomena

Oxygen

Silicon

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