Erlangen 2022 – scientific programme

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K: Fachverband Kurzzeit- und angewandte Laserphysik

K 6: Laser-Beam Matter Interaction - Laser Applications I

K 6.1: Invited Talk

Thursday, March 17, 2022, 10:30–11:00, K-H4

Front and rear surface ablation within gold films with variable film thickness induced by ultrafast laser radiation — •Markus Olbrich, Theo Pflug, and Alexander Horn — Laserinstitut Hochschule Mittweida, Technikumplatz 17, 09648 Mittweida

Irradiating gold films with a different film thickness (d_z = 100 - 8000 nm) on a glass substrate (d_z ≈ 1 mm) with single-pulsed ultrafast laser radiation (τ_H = 40 fs, λ = 800 nm) results in different ablation structures in dependence on the applied peak fluence H₀. Thereby, for thin films (d_z ≤ 200 nm) the complete film is removed, whereby for thicker films ablation structures featuring a cupola-like shape with a height of several microns are observed. The ablation structures are explained by two-temperature hydrodynamic modeling (TTMHD) identifying the interplay of front and rear surface ablation as the origin. The formation of the ablation structures is induced either by spallation and phase explosion at the front surface, and at the rear surface by the propagation of the emitted shock and rarefaction waves, generating also spallation. The performed simulations are validated by ultrafast time and space resolved reflectometry (τ_H = 60 fs, λ = 440 nm, and λ = 480 nm) at both surfaces of the films within a self-developed optical setup. The complementary combination of reflectometry at the front and rear surfaces portrays the dynamics of the induced temperature and pressure distributions as well as the dynamics of the front and rear surface by comparing the measured relative change of reflectance Δ R/R to the simulated dynamics of the named parameters.