Speaker
Description
In nature, high-pressure phases of silica are found in meteoritic craters resulting from high-velocity impacts. Studying these phases in a laboratory setting remains a tedious task, as it requires high-pressure generation, from tens of Giga-Pascal (GPa) to Tera-Pascal (TPa). Diamond anvil cell (DAC) is commonly used for high-pressure generation but suffers from intrinsic limitations of volume and processing time restrictions [1]. On the other hand, femtosecond lasers can be used as a tool for mimicking high-pressure impacts, as demonstrated in sapphire using single spot experiments [2].
However, these techniques provide a modified zone as a result of laser-matter interaction, and the material is not exclusively subjected to intense pressure waves, but also to photo-induced effects, making the interpretation of the outcome difficult.
Here, we recreated high-pressure phases in fused silica using a double-beam ultrafast laser exposure scheme. The basic idea is to separate spatially zones under laser exposure from zones subjected to high-pressure conditions. This non-contact method offers a powerful alternative to classical methods used to investigate high-pressure phases in materials. Raman analysis of zones that experienced high-pressure, indicates structural changes comparable to mechanically-induced densification. Further, we have conducted volume variation measurements using a cantilever-deflection method [3] and investigated pressure-induced chemical etching enhancement effects. In a nutshell, we have demonstrated that spatially separated femtosecond pulses create the condition for high-pressure densification, possibly up to 10 GPa, exclusively due to interfering shock waves emitted from the two foci.
References
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P. Richet and P. Gillet, "Pressure-induced amorphization of minerals: a review," Eur. J. Mineral 9, 907-933 (1997).
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S. Juodkazis et.al, "Laser-Induced Microexplosion Confined in the Bulk of a Sapphire Crystal: Evidence of Multimegabar Pressures," Phys. Rev. Lett. 96, 166101–4 (2006).
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Yves Bellouard et. al, "Stress-state manipulation in fused silica via femtosecond laser irradiation," Optica 3, 1285-1293 (2016)
| Speaker Country | Switzerland |
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