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Wright, C. David
in Cooperation with on an Cooperation-Score of 37%
Topics
Publications (8/8 displayed)
- 2024Probabilistic Photonic Computing with Chaotic Light
- 2022Propagation dynamics of the solid–liquid interface in Ge upon ns and fs laser irradiationcitations
- 2021Enhanced Performance and Diffusion Robustness of Phase-Change Metasurfaces via a Hybrid Dielectric/Plasmonic Approachcitations
- 2019A Nonvolatile Phase‐Change Metamaterial Color Displaycitations
- 2016Design of practicable phase-change metadevices for near-infrared absorber and modulator applicationscitations
- 2014An optoelectronic framework enabled by low-dimensional phase-change films.citations
- 2012Crystallization of Ge2Sb2Te5 films by amplified femtosecond optical pulsescitations
- 2008Fast simulation of phase-change processes in chalcogenide alloys using a Gillespie-type cellular automata approachcitations
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article
Propagation dynamics of the solid–liquid interface in Ge upon ns and fs laser irradiation
Abstract
<jats:title>Abstract</jats:title><jats:p>Monitoring the laser-induced melting and solidification dynamics of Ge upon laser irradiation is an enormous challenge due to the short penetration depth of its liquid phase. In this work, real-time pump-probe experiments in combination with finite element calculations have been employed to investigate the melting and solidification dynamics of germanium upon ns and fs laser pulse irradiation (<jats:italic>λ</jats:italic> = 800 nm). Excellent agreement between experiments and simulations allowed us to indirectly determine additional time- and depth-dependent information about the transformation dynamics of germanium, including the thickness evolution of the molten layer, as well as its melting and solidification velocities for the two pulse durations for different fluences. Our results reveal considerable differences in the maximum thickness of the molten Ge superficial layers at sub-ablative fluences for ns and fs pulses, respectively. Maximum melt-in velocities of 39 m s<jats:sup>−1</jats:sup> were obtained for ns pulses at high fluences, compared to non-thermal melting of a thin layer within 300 fs for fs pulses already at moderate fluences. Maximum solidification velocities were found to be 16 m s<jats:sup>−1</jats:sup> for ns pulses, and up to 55 m s<jats:sup>−1</jats:sup> for fs pulses. Weak signs of amorphization were observed for fs excitation, suggesting that the lower limit of solidification velocities for a complete amorphization is above 55 m s<jats:sup>−1</jats:sup>. In addition, we show high precision measurements of the melt-in velocities over the first 20 nm by means of fs microscopy with sub-ps temporal resolution. Here, differences of the melt-in process of several orders of magnitude were observed, ranging from virtually instantaneous melting within less than 2 ps even for a moderate peak fluence up to 200 ps for fluences close to the melting threshold.</jats:p>