Bonn 2025 – scientific programme

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MO: Fachverband Molekülphysik

MO 19: Interaction with Strong or Short Laser Pulses I (joint session A/MO)

MO 19.1: Invited Talk

Wednesday, March 12, 2025, 14:30–15:00, GrHS Mathe

Time Resolved Diffractive Imaging of Laser Induced Dynamics in Materials — •Tom Böttcher, Richard Altenkirch, Stefan Lochbrunner, Christian Peltz, Thomas Fennel, and Franziska Fennel — Institute of Physics and Department of Life, Light and Matter, University of Rostock, 18051 Rostock, Germany

Micromachining with ultrashort laser pulses is widely used for industrial applications. In contrast to picosecond and nanosecond lasers, ultrashort laser pulses allow precise material modifications due to local electronic excitation on timescales well below electron-ion equilibration times and thermal dissipation. However, the underlying processes leading to target modification and ablation after ultrashort laser pulse excitation are still insufficiently understood.

We present an experimental method to study the excitation and relaxation processes in thin gold films using femtosecond to nanosecond single-shot pump probe coherent diffractive imaging. The target is a 30 nm-thick, free-standing gold foil, which is excited using an 800 nm femtosecond pump pulse. The dynamics in the excited foil are imaged after a variable time delay using a 400 nm femtosecond probe pulse which creates a diffraction image that is captured by a CMOS camera. A phase retrieval algorithm is used to reconstruct the 2D spatial and time resolved exit field at the target position from the captured diffraction images. Dynamics are monitored up to 2 ns, providing access to ultrafast excitation (fs-ps regime) as well as melting and ablation dynamics (ps-ns regime).

Keywords: Coherent Diffractive Imaging; In-Line Holography; Laser Ablation; Phase Retrieval; Ultrashort Laser Pulses