Laser thin film ablation with multiple beams and tailored beam profiles

Rung, Stefan; Bischoff, Christian; Jäger, Erwin; Umhofer, Udo; Hellmann, Ralf

doi:10.1117/12.2038572

Cited by 5 publications

(6 citation statements)

References 7 publications

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“…As a result, the material adjacent to the ablation region has to absorb less energy, which, in turn, reduces the undesired modifications of the remaining thin film properties [6]. Besides these benefits resulting from the intensity plateau and the steep wings of the intensity distribution, the transformation of a round laser footprint into a rectangular footprint can additionally improve the scribing process significantly, as illustrated in Figure 1b [7]. Whereas a pulsed laser with a round laser footprint generates a saw tooth pattern along the rim of an ablated line, a rectangular laser footprint circumvents such a pattern.…”

Section: Introductionmentioning

confidence: 99%

“…However, contrary to the idealized representation of the laser scribed line consisting of a series of perfectly rectangular-shaped laser footprints shown in Figure 1b, the ablation spot of a single laser pulse will display deviations from the rectangular geometry, such as, e.g., rounding at the corners. For laser micromachining application, often, diffractive Top-Hat beam shaping optics are employed [1,2,6,7]. The resulting laser beam profile of such diffractive beam shapers depends strongly on, e.g., the position of the working plane, the free aperture of the beam delivery path and, certainly, on the adjustment of the beam shaper itself.…”

Section: Introductionmentioning

confidence: 99%

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

2014

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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.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

2014

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“…Topag Lasertechnik GmbH introduced a new beam shaping concept, the so called focused beam shaping (FBS) for transforming a Gaussian beam into a rectangular or circular top hat beam profile 6 . The design is based on a diffractive beam shaping concept but it is realized by a smooth phase-modulating surface profile.…”

Section: Introductionmentioning

confidence: 99%

Manufacture of refractive and diffractive beam-shaping elements in higher quantities using glass molding technology

Wolz¹,

Blöcher²,

Dross³

et al. 2015

SPIE Proceedings

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Laser beam shaping elements can be used e.g. for material processing. The results of these processes can be improved when the usually Gaussian profile of the laser is transformed into a top hat profile, which can be circular or rectangular in shape. Another frequently used type of beam-forming devices are beam splitters for parallel processing using only one laser. These types of beam formers can be implemented as diffractive or refractive elements. So far these optics are produced either directly by means of lithography e.g. in glass or in plastic using a hot embossing process or nanoimprint technology..Elements produced in this way have either the disadvantage of high costs or they are limited in temperature range, laser power or wavelength. A newly developed molding process for glass allows the manufacture of larger numbers of optics with reduced cost.The production of molds for refractive top hat beam shaping devices requires very high precision of the applied grinding process. Form deviations below 100 nm are necessary to obtain a homogeneous illumination. Measurements of the surface topography of gauss to top hat beam shaping elements using white light interferometry are presented as well as results of optical measurements of the beam profile using a camera.Continuous diffractive beam shaping elements for beam splitting applications are designed to generate several sub-beams each carrying the same energy. In order to achieve this, form deviations of less than 50 nm are required. Measurements of the surface of a 1 x 5 beam splitter are compared with ideal beam splitter profiles. The resulting beam intensity distribution of a molded element is presented.

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“…In contrast, a Gaussian shaped intensity distribution can be disadvantageous in several micromachining applications. Flanks of a Gaussian intensity distribution below the ablation threshold induce heat in the workpiece leading to heat affected zones (HAZ) which are undesired as, e.g., they lead to a lower electrical performance in manufacturing of solar cells [8]. The wear resistance of carbon-based coatings suffers from HAZ, too [9].…”

Section: Introductionmentioning

confidence: 99%

Tailored laser beam shaping for efficient and accurate microstructuring

et al. 2018

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Large-area processing with high material removal rates by ultrashort pulsed (USP) lasers is coming into focus by the development of high-power USP laser systems. However, currently the bottleneck for high-rate production is given by slow and inefficient beam manipulation. On the one hand, slow beam deflection with regard to high pulse repetition rates leads to heat accumulation and shielding effects, on the other hand, a conventional focus cannot provide the optimum fluence due to the Gaussian intensity profile. In this paper, we emphasize on two approaches of dynamic laser beam shaping with liquid crystal on silicon spatial light modulation and acousto-optic beam shaping. Advantages and limitations of dynamic laser beam shaping with regard to USP laser material processing and methods for reducing the influence of speckle are discussed. Additionally, the influence of optics induced aberrations on speckle characteristics is evaluated. Laser material processing results are presented correlating the achieved structure quality with the simulated and measured beam quality. Experimental and analytical investigations show a certain fluence dependence of the necessary number of alternative holograms to realize homogeneous microstructures.

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Laser thin film ablation with multiple beams and tailored beam profiles

Cited by 5 publications

References 7 publications

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

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

Manufacture of refractive and diffractive beam-shaping elements in higher quantities using glass molding technology

Tailored laser beam shaping for efficient and accurate microstructuring

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