• Khalil, Alain Abou
• Bon, Pierre
• Aldeiturriaga, David Pallares
• Sedao, Xxx
• Mauclair, Cyril
• Aguilar, Alberto

Abstract

<jats:title>Abstract</jats:title><jats:p>Ultrafast laser processing can induce surface nanostructurating (SNS) in most materials with dimensions close to the irradiation laser wavelength. In-situ SNS characterization could be key for laser parameter’s fine-tuning, essential for the generation of complex and/or hybrid nanostructures. Laser Induced Periodic Surface Structures (LIPSS) created in the ultra-violet (UV) range generate the most fascinating effects. They are however highly challenging to characterize in a non-destructive manner since their dimensions can be as small as 100 nm. Conventional optical imaging methods are indeed limited by diffraction to a resolution of <jats:inline-formula><jats:alternatives><jats:tex-math> 150</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>≈</mml:mo><mml:mn>150</mml:mn></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> nm. Although optical super-resolution techniques can go beyond the diffraction limit, which in theory allows the visualization of LIPSS, most super-resolution methods require the presence of small probes (such as fluorophores) which modifies the sample and is usually incompatible with a direct surface inspection. In this paper, we demonstrate that a modified label-free Confocal Reflectance Microscope (CRM) in a photon reassignment regime (also called re-scan microscopy) can detect sub-diffraction limit LIPSS. SNS generated on a titanium sample irradiated with a <jats:inline-formula><jats:alternatives><jats:tex-math> =257</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>λ</mml:mi><mml:mo>=</mml:mo><mml:mn>257</mml:mn></mml:mrow></mml:math></jats:alternatives></jats:inline-formula> nm femtosecond UV-laser were characterized with nanostructuring period ranging from 105 to 172 nm. Our label-free, non-destructive optical surface inspection was done at 180 <jats:inline-formula><jats:alternatives><jats:tex-math></jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>μ</mml:mi></mml:math></jats:alternatives></jats:inline-formula>m<jats:inline-formula><jats:alternatives><jats:tex-math>^2</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msup><mml:mrow /><mml:mn>2</mml:mn></mml:msup></mml:math></jats:alternatives></jats:inline-formula>/s, and the results are compared with commercial SEM showing the metrological efficiency of our approach.</jats:p>

Topics

• impedance spectroscopy
• surface
• scanning electron microscopy
• theory
• titanium