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

TL;DR

This paper presents a method for fabricating high-fidelity glass micro-axicons using laser-assisted wet etching and laser polishing, enabling precise control of their optical properties for generating quasi-Bessel beams.

Contribution

The authors demonstrate a novel fabrication process combining femtosecond laser writing, KOH etching, and CO2 laser polishing to produce micro-axicons with smooth surfaces and controlled tip curvature.

Findings

Micro-axicons produce quasi-Bessel beams with 5.3 μm diameter.

The generated beams maintain their diameter over 3.5 mm.

The fabrication process achieves high fidelity and surface smoothness.

Abstract

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 {\mu}m. It is then shown with 500 {\mu}m-diameter axicons that the quasi-Bessel beam is generated closely after the tip, and features a 5.3 {\mu}m diameter maintained over a propagation distance of almost 3.5 mm.