Photoexcitation Dynamics in Dielectrics Irradiated by Ultrafast Laser Pulses

This PhD project is embedded within the broader scope of the FLASH project, which aims to predict and model structural transformations in dielectric materials irradiated by bursts of ultrafast laser pulses, with durations ranging from femtoseconds to several nanoseconds. The work focuses on two major challenges in the physics of ultrafast laser-matter interaction: (1) understanding the nonlinear absorption dynamics governed by photoexcited states, and (2) modeling the inhomogeneous thermal relaxation in porous and heterogeneous media.

To address these challenges, the candidate will contribute to the development of a quantum-mechanical model for nonlinear light absorption based on Maxwell-Bloch Equations (MBE), combined with ab initio calculations of band structures and transition dipole moments using DFT codes (Abinit, VASP, Octopus, SALMON). The materials of interest are functional dielectrics, such as fused silica (SiO₂), alumina (Al₂O₃), and zirconia (ZrO₂), relevant for emerging 3D photonic technologies.

The project will provide both theoretical insight and numerical tools for predicting the optical and structural evolution of photoexcited dielectrics and for benchmarking these models against ultrafast time-resolved experiments carried out at national LUMA platforms.

Scientific Objectives:

The PhD research will focus on the following main objectives:

1. Modeling photoexcitation dynamics in key dielectric materials using a quantum approach (MBE) informed by high-resolution band structure and dipole moment data.
2. Developing a database of optical properties (e.g., refractive index, nonlinear susceptibilities) for selected materials in both ground and photoexcited states.
3. Validating theoretical predictions through comparison with time-resolved spectroscopy and imaging experiments conducted within the Ultrafast LUMA infrastructure.
4. Investigating the coupling of electronic excitation and structural effects, including bandgap renormalization and transient polymorphism in irradiated porous dielectrics.