Characterization of Laser Beam Shaping Optics Based on Their Ablation Geometry of Thin Films

Micromachines

Stefan Rung¹  Johannes Barth²  Ralf Hellmann²  Maria Farsari² 

[1] University of Applied Science Aschaffenburg, Wuerzburger Strasse 45, D-63743 Aschaffenburg, Germany;

关键词: laser beam shaping;    diffractive optical element (DOE);    Top-Hat;    transparent conductive oxides (TCO);    indium tin oxide (ITO);    thin film;    laser ablation;   

DOI  :  10.3390/mi5040943

来源: mdpi

【 摘 要 】

Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam profile depends strongly on the beam alignment of the entire laser system. In particular, the adjustment of the beam shaping element is of upmost importance. For an appropriate alignment of the beam shaper, it is generally necessary to observe the intensity distribution near the focal position of the applied focusing optics. Systems with a low numerical aperture (NA) can commonly be qualified by means of laser beam profilers, such as a charge-coupled device (CCD) camera. However, laser systems for micromachining typically employ focus lenses with a high NA, which generate focal spot sizes of only several microns in diameter. This turns out to be a challenge for common beam profiling measurement systems and complicates the adjustment of the beam shaper strongly. In this contribution, we evaluate the quality of a Top-Hat beam profiling element and its alignment in the working area based on the ablated geometry of single pulse ablation of thin transparent conductive oxides. To determine the best achievable adjustment, we develop a quality index for rectangular laser ablation spots and investigate the influences of different alignment parameters, which can affect the intensity distribution of a Top-Hat laser beam profile.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.