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High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams

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ABSTRACT

Femtosecond pulses provide an extreme degree of confinement of light matter-interactions in high-bandgap materials because of the nonlinear nature of ionization. It was recognized very early on that a highly focused single pulse of only nanojoule energy could generate spherical voids in fused silica and sapphire crystal as the nanometric scale plasma generated has energy sufficient to compress the material around it and to generate new material phases. But the volumes of the nanometric void and of the compressed material are extremely small. Here we use single femtosecond pulses shaped into high-angle Bessel beams at microjoule energy, allowing for the creation of very high 100:1 aspect ratio voids in sapphire crystal, which is one of the hardest materials, twice as dense as glass. The void volume is 2 orders of magnitude higher than those created with Gaussian beams. Femtosecond and picosecond illumination regimes yield qualitatively different damage morphologies. These results open novel perspectives for laser processing and new materials synthesis by laser-induced compression.

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Related in: MedlinePlus

SEM image of the cross section of the void channel of Fig. 1(a) at the position of the white dashed line.The cross section was revealed by transverse FIB milling of the lower part of the void. The laser electric field is polarized along y direction. (left) Schematic reconstructed cross-section profile with measurements.
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f3: SEM image of the cross section of the void channel of Fig. 1(a) at the position of the white dashed line.The cross section was revealed by transverse FIB milling of the lower part of the void. The laser electric field is polarized along y direction. (left) Schematic reconstructed cross-section profile with measurements.

Mentions: We carefully examined the cross section of the channels and Fig. 3 shows an image of the transverse section of the void structure shown at the position of the white dashed line in Fig. 1.


High aspect ratio micro-explosions in the bulk of sapphire generated by femtosecond Bessel beams
SEM image of the cross section of the void channel of Fig. 1(a) at the position of the white dashed line.The cross section was revealed by transverse FIB milling of the lower part of the void. The laser electric field is polarized along y direction. (left) Schematic reconstructed cross-section profile with measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5037470&req=5

f3: SEM image of the cross section of the void channel of Fig. 1(a) at the position of the white dashed line.The cross section was revealed by transverse FIB milling of the lower part of the void. The laser electric field is polarized along y direction. (left) Schematic reconstructed cross-section profile with measurements.
Mentions: We carefully examined the cross section of the channels and Fig. 3 shows an image of the transverse section of the void structure shown at the position of the white dashed line in Fig. 1.

View Article: PubMed Central - PubMed

ABSTRACT

Femtosecond pulses provide an extreme degree of confinement of light matter-interactions in high-bandgap materials because of the nonlinear nature of ionization. It was recognized very early on that a highly focused single pulse of only nanojoule energy could generate spherical voids in fused silica and sapphire crystal as the nanometric scale plasma generated has energy sufficient to compress the material around it and to generate new material phases. But the volumes of the nanometric void and of the compressed material are extremely small. Here we use single femtosecond pulses shaped into high-angle Bessel beams at microjoule energy, allowing for the creation of very high 100:1 aspect ratio voids in sapphire crystal, which is one of the hardest materials, twice as dense as glass. The void volume is 2 orders of magnitude higher than those created with Gaussian beams. Femtosecond and picosecond illumination regimes yield qualitatively different damage morphologies. These results open novel perspectives for laser processing and new materials synthesis by laser-induced compression.

No MeSH data available.


Related in: MedlinePlus