Pulse-to-pulse ultrafast dynamics of highly photoexcited Ge2Sb2Te5 thin films

Observing ultrafast pulse-to-pulse dynamics of highly photoexcited materials could foster a comprehensive understanding of the initial stage of irreversible photoinduced events, such as phase change, structural deformation, and laser ablation. In this study, using high-repetition-rate single-shot sp...

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Bibliographic Details
Published in:Japanese Journal of Applied Physics 2023-02, Vol.62 (2), p.022001
Main Authors: Kobayashi, Masataka, Arashida, Yusuke, Asakawa, Kanta, Kaneshima, Keisuke, Kuwahara, Masashi, Konishi, Kuniaki, Yumoto, Junji, Kuwata-Gonokami, Makoto, Takeda, Jun, Katayama, Ikufumi
Format: Article
Language:English
Subjects:
Decay
Density
Laser ablation
laser induced periodic surface structures
Lasers
phase change material
Phase transitions
Photoexcitation
singleshot diagnostics
Thin films
Transmittance
ultrafast spectroscopy
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Summary:Observing ultrafast pulse-to-pulse dynamics of highly photoexcited materials could foster a comprehensive understanding of the initial stage of irreversible photoinduced events, such as phase change, structural deformation, and laser ablation. In this study, using high-repetition-rate single-shot spectroscopy and a laser microscope, the pulse-to-pulse ultrafast dynamics of energy relaxation in Ge2Sb2Te5 thin films are revealed under high-density photoexcitation that induces sequential events involving the crystalline-to-amorphous phase transition, melt and quench processes, and formation of laser-induced periodic surface structures (LIPSSs). Above the threshold excitation density for LIPSS formation, the first excitation pulse induces the transient transmittance change of the crystalline phase in a picosecond timescale, and subsequent pulses provoke the amorphous phase energy relaxation with a long decay time of hundreds of picoseconds. We observed that the subsequent pulses gradually reduce the amplitude and decay time of the transient transmittance, leading to efficient energy relaxation and LIPSS formation in the photoinduced amorphous phase.
ISSN:0021-4922
1347-4065
DOI:10.35848/1347-4065/acb476