Mainz 2026 – scientific programme

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K: Fachverband Kurzzeit- und angewandte Laserphysik

K 1: Laser Systems and their Applications I

K 1.4: Talk

Monday, March 2, 2026, 12:30–12:45, HS 20

Laser-induced processes during and after the laser-matter interaction of single-crystalline silicon irradiated with ultrashort pulsed laser radiation — •Andy Engel, Markus Olbrich, Theo Pflug, and Alexander Horn — Laserinstitut Hochschule Mittweida, Technikumplatz 17, 09648 Mittweida, Germany

The irradiation of single-crystalline silicon with ultrashort pulsed laser radiation leads to irreversible material changes when a material-dependent threshold is exceeded, starting with changes in crystallinity and extending to ablation. This work examines these material transformations for the irradiation of single-crystalline, <111>-oriented silicon as a function of both the fluence of the applied ultrashort pulsed laser radiation (40 fs, 800 nm) and the number of individual pulses delivered to each processing spot. The irreversible changes arising from the interaction between laser radiation and matter were identified by measuring the spatially and spectrally resolved refractive index using ex-situ ellipsometry and SEM analyses. Comparative investigations of the surface topography of the irradiated regions were conducted via confocal laser scanning microscopy and atomic force microscopy. Additional insights into the depth of thermally induced material alterations were obtained through subsequent wet chemical etching. When combined with ultrafast metrology, pump-probe imaging reflectometry, and interferometry, these methods enable a more comprehensive and precise characterization of the physical processes triggered by ultrashort pulsed laser irradiation.

Keywords: ellipsometry; laser matter interaction; ultrashort pulsed laser radiation; phase change; pump-probe