Among recent advanced manufacturing techniques introduced over the last decades, non-ablative femtosecond laser processing has gained a lot of attention thanks to its applicability to a variety of substrates and its unique ability to locally process transparent materials in their volumes. The laser-induced taxonomy of structural modifications is rich and, despite the extreme brevity of the laser-matter interaction, includes nano-crystallization events as recently reported in various amorphous substrates. Yet, the mechanism leading to these nano-crystallization phenomena driven by locally extreme exposure conditions, similar to warm-dense state of matter (WDM), remains elusive.
We present in situ nano-crystallization dynamics using X-ray microdiffraction, reporting such experiments for the first time to our knowledge. Specifically, we investigate the case of a femtosecond laser-induced nano-crystallization process in an amorphous multilayer stack of Al2O3/Nb2O5 layers using operando X-ray micro-diffraction at the microXAS beamline of the Swiss Light Source (SLS). We identify the crystalline phases and the timescales of the transition using varying laser exposure conditions.
KEYWORDS: Near field optics, Glasses, Femtosecond phenomena, Etching, Wet etching, Ultrafast lasers, Silica, Raman spectroscopy, Nanostructuring, Near field
Multilayer dielectric materials are used to tailor the optical properties of interfaces. While laser damage resistant coatings have been carefully investigated, the potential of laser modifications in staked alternating dielectric layers has not been explored thoroughly.
Here, we investigate the effects of ultrafast laser exposure on alternating stacks of SiO2 and SiNx dielectric films deposited on a substrate, focusing primarily on non-ablative exposure and on its effect on the layer intermixing and the resultant change of material properties. We are especially interested on the experimental characterization of the materials after femtosecond laser exposure, particularly on the post-exposure material structure.
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