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We present here a nanosecond laser ablation of Si(111) wafer withdiffraction-free (Bessel-$J_0$) beams. First, the Axicon a conical shapedoptical element for beam shaping is characterized with a visible and infraredlight sources. Then, ablation profiles are obtained with Bessel beams generatedfor $\alpha=1^{\circ}$ and $\alpha=20^{\circ}$ base angles, then they arecharacterized via a Scanning Electron, an Atomic Force and an OpticalInterferometric Microscopes. Experimental results compared with theoreticalpredictions obtained by using Bessel functions. Results show that Bessel beamsgive possibility of straightforward micro-structuring of Si(111) samplesbecause the only central spot of Bessel beams could damage the surface providedthat the laser pulse energy becomes in energy-range we found in ourexperiments. Moreover, our results clearly indicate that reduced HAZ area dueto thermal expansion in ns pulse regime are natural outcome of Bessel beams asopposed to Gauss beams of same spot size. Lastly, nanosecond pulses indicatetwo-ablation regimes regarding the pulse energy, the quality of structures canbe enhanced by using high quality Gauss beams ($M^{2}\approx1$) and the size offabricated structures can be much reduced by using larger base angle of Axicon(such as $\alpha=40^{\circ}$) in our scheme.

Direct micro-structuring of Si(111) surfaces through nanosecond-laser Bessel beams