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High-fidelity glass micro-axicons fabricated by laser-assisted wet etching

We report on the fabrication of micro-axicons made of glass by laser-assisted wet etching (LAE) and laser polishing. The employed technique, relying on an efficient direct-writing process by femtosecond laser, allows revealing high fidelity profiles while etched in a heated potassium hydroxide (KOH) solution. The remaining surface roughness is then smoothened by carbon dioxide (CO2) laser polishing. Such polishing is limited to the skin of the component so that the tip is only slightly rounded, with a radius of curvature of nearly 200 μm. It is then shown with 500 μm-diameter axicons that the quasi-Bessel beam is generated closely after the tip, and features a 5.3 μm diameter maintained over a propagation distance of almost 3.5 mm.