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.
In this contribution, we compare the etching behaviour of fused silica machined with a femtosecond laser at three different wavelengths. We use a high-power YAG laser to generate 450 fs-long pulses at the first (1030 nm) and third (343 nm) harmonic. We demonstrate how these new machining techniques can be used to improve the laser-assisted etching in fused silica not only in terms of etching speed, but also in terms of minimal feature size and surface roughness. Processing speeds of several 100 mm/s become possible due to the new regime using fs-UV light.
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