Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 79: Ultrafast Electron Dynamics III

O 79.8: Talk

Thursday, March 20, 2025, 12:15–12:30, H2

Ultrafast Photoexcitation of Semiconducting Photocathode Materials: An Ab Initio Study — •Hilde Bellersen, Michele Guerrini, and Caterina Cocchi — Carl von Ossietzky Universität Oldenburg, Institute of Physics, 26129 Oldenburg, Germany

Cs-based semiconductors like Cs₃Sb and Cs₂Te are currently used as photocathode materials in particle accelerators. Their performance as electron sources critically depends on their response to the intense laser radiation impinging them. In this work, we investigate from first principles the time-dependent response of Cs₃Sb and Cs₂Te to ultrafast laser pulses of varying intensities, ranging from 1 GW/cm² to 100 TW/cm². Nonlinear effects, including high harmonic generation and multiphoton absorption, emerge at thresholds of 400 GW/cm² for Cs₃Sb and 500 GW/cm² for Cs₂Te. Beyond these intensities, the energy uptake and number of excited electrons saturate, with renewed increases observed beyond 10 TW/cm². These findings provide new insights into the nonlinear optical properties of Cs₃Sb and Cs₂Te, contributing to the optimization of these materials for the development of next-generation photoinjectors.

Keywords: photocathodes; time-dependent density functional theory; nonlinear optics; ultrafast dynamics