One-step fabrication of annular microstructures based on improved femtosecond laser Bessel–Gaussian beam shaping

In this work, a favorable approach is proposed for the high-efficiency fabrication of annular microstructures by shaping femtosecond Gaussian laser into Bessel–Gaussian beam. An adjustable annular beam is generated by a combination of an axicon, a lens, and an objective. Uniform annular microstructures are fabricated on the surface of fused silica in a single illumination step with only one pulse and without stage translation, the parameters of which are coincident with theoretical design. By adjusting the relative distance between the lens and objective, the diameters of the annular microstructures can be flexibly controlled in a wide range. In addition, it has been discussed that the effects of laser pulse energy and off-focus on the depth and line-width of the fabricated annuli.