Engraving Depth‐Controlled Nanohole Arrays on Fused Silica by Direct Short‐Pulse Laser Ablation

Abstract

AbstractPeriodic nanohole arrangements constitute an important building block of advanced photonic devices. Aside from standard nanofabrication tools, a direct laser‐based approach is introduced here, that enables single‐step and point‐by‐point machining of arrays of holes with subwavelength diameters and depths reaching several micrometers at the surface of fused silica. The method relies on a simple optical arrangement including an axicon combined with an amplitude mask to shape the laser intensity in appropriately truncated micro‐Bessel beams of adjustable length. The suitability and limitations of the technique are investigated to fabricate arrays of cylindrical nanoholes with tunable depths. In particular, the challenge of avoiding crosstalk effects during the laser‐writing process of high‐density arrays is explored. The achievability of square arrays of nanoholes at the surface of fused silica, with diameters down to 200 nm and variable depths from 3 to 20 µm at a spatial density defined by a pitch of 1.5 µm is demonstrated. The performance level shows the potential of the direct‐laser‐processing method towards the realization of integrated devices, offering a highly flexible and cost‐effective alternative technique to current nanofabrication methods.