Tailored focal beam shaping and its application in laser material processing

Möhl, Anna; Kaldun, Sebastian; Kunz, Clemens; Müller, Frank A.; Fuchs, Ulrike

doi:10.2351/1.5123051

Cited by 38 publications

(24 citation statements)

References 30 publications

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“…The most common approach for shaping focal intensity distributions is based on Fourier optics, where the focusing optics transforms the incoming beam profile into the desired shape. This is well-explained for rotational symmetry in [19,22]. However, for non-rotationally symmetric focal intensity distributions, the symmetry of the beam-shaping element needs to be broken, while the focusing optics remains the same.…”

Section: Focal Beam-shaping and Characterizationmentioning

confidence: 84%

Squared Focal Intensity Distributions for Applications in Laser Material Processing

Wilms¹,

Fuchs²,

Müller

et al. 2021

Materials

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Tailored intensity profiles within the focal spot of the laser beam offer great potential for a well-defined control of the interaction process between laser radiation and material, and thus for improving the processing results. The present paper discusses a novel refractive beam-shaping element that provides different squared intensity distributions converted from the Gaussian output beam of the utilized femtosecond (fs) laser. Using the examples of surface structuring of stainless-steel on the micro- and nano-scale, the suitability of the beam-shaping element for fs-laser material processing with a conventional f-Theta lens is demonstrated. In this context, it was shown that the experimental structuring results are in good agreement with beam profile measurements and numerical simulations of the beam-shaping unit. In addition, the experimental results reveal the improvement of laser processing in terms of a significantly reduced processing time during surface nano-structuring and the possibility to control the ablation geometry during the fabrication of micro-channels.

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Section: Focal Beam-shaping and Characterizationmentioning

confidence: 84%

Squared Focal Intensity Distributions for Applications in Laser Material Processing

Wilms¹,

Fuchs²,

Müller

et al. 2021

Materials

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“…The most frequent period in the cross section of the 2D-FFT spectrum is about 2.75 cm −1 , which corresponds to a spatial period of about 362 nm. The homogeneity can be improved by using top-hat beam profiles, but this was not the subject of the current work [ 43 , 44 ]. Nevertheless, the results demonstrate that a thin gold layer enables the reliable and reproducible fabrication of HSFL on large surfaces areas without damaging the fused silica substrate.…”

Section: Resultsmentioning

confidence: 99%

Large-Area Fabrication of Laser-Induced Periodic Surface Structures on Fused Silica Using Thin Gold Layers

et al. 2020

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Despite intensive research activities in the field of laser-induced periodic surface structures (LIPSS), the large-area nanostructuring of glasses is still a challenging problem, which is mainly caused by the strongly non-linear absorption of the laser radiation by the dielectric material. Therefore, most investigations are limited to single-spot experiments on different types of glasses. Here, we report the homogeneous generation of LIPSS on large-area surfaces of fused silica using thin gold layers and a fs-laser with a wavelength λ = 1025 nm, a pulse duration τ = 300 fs, and a repetition frequency frep = 100 kHz as radiation source. For this purpose, single-spot experiments are performed to study the LIPSS formation process as a function of laser parameters and gold layer thickness. Based on these results, the generation of large-area homogenous LIPSS pattern was investigated by unidirectional scanning of the fs-laser beam across the sample surface using different line spacing. The nanostructures are characterized by a spatial period of about 360 nm and a modulation depth of around 160 nm. Chemical surface analysis by Raman spectroscopy confirms a complete ablation of the gold film by the fs-laser irradiation. The characterization of the functional properties shows an increased transmission of the nanostructured samples accompanied by a noticeable change in the wetting properties, which can be additionally modified within a wide range by silanization. The presented approach enables the reproducible LIPSS-based laser direct-writing of sub-wavelength nanostructures on glasses and thus provides a versatile and flexible tool for novel applications in the fields of optics, microfluidics, and biomaterials.

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“…This is done with a theoretical approximation given by Eq. (5). Consequently, at this plane instead of p(x, y) one gets the retrieved pupil p ret (x, y) (or p ret (r) in polar coordinates).…”

Section: Numerical Simulations Of Complex Beam Shapingmentioning

confidence: 99%

“…Several efforts to achieve full control over amplitude, phase and polarization of light focused with high numerical aperture objective lenses have been carried out [1][2][3][4]. Furthermore, within the framework of the scalar theory of diffraction some alternative focal beam shaping methods, valid under the paraxial approximation, have also demonstrated their usefulness in many practical applications [5][6][7]. Several types of pure amplitude pupils were used to increase the depth of focus and/or control the distribution of light near the focus.…”

Section: Introductionmentioning

confidence: 99%

Complex shaping of the depth of focus

Mendoza-Yero

2020

OSA Continuum

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In this manuscript an exact solution to the inverse problem of axial beam shaping along the focus of a convergent lens is found. This allows to extend, within the framework of the scalar theory of diffraction, the mathematical formalism of complex pupils to include axial phase modulation. Numerical simulations based on Fourier transform as well as convolution operations indicate that amplitude and phase modulation can be performed simultaneously. It is also shown that include or not phase modulation in the beam shaping process can increase its efficiency more than three times. In addition, an analytical expression for the Gouy phase that depends on the introduced phase modulation was also derived. It is expected that obtained results benefit many photonic applications involving the control and manipulation of light along the focal region.

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Tailored focal beam shaping and its application in laser material processing

Cited by 38 publications

References 30 publications

Squared Focal Intensity Distributions for Applications in Laser Material Processing

Squared Focal Intensity Distributions for Applications in Laser Material Processing

Large-Area Fabrication of Laser-Induced Periodic Surface Structures on Fused Silica Using Thin Gold Layers

Complex shaping of the depth of focus

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