Micromachining of Alumina Using a High-Power Ultrashort-Pulsed Laser.

We report on a comprehensive study of laser ablation and micromachining of alumina using a high-power 1030 nm ultrashort-pulsed laser. By varying laser power up to 150 W, pulse duration between 900 fs and 10 ps, repetition rates between 200 kHz and 800 kHz), spatial pulse overlap between 70% and 80% and a layer-wise rotation of the scan direction, the ablation efficiency, ablation rate and surface roughness are determined and discussed with respect to an efficient and optimized process strategy. As a result, the combination of a high pulse repetition rate of 800 kHz and the longest evaluated pulse duration of 10 ps leads to the highest ablation efficiency of 0.

Ultrashort Pulsed Laser Drilling of Printed Circuit Board Materials.

We report on a comprehensive study of laser percussion microvia drilling of FR-4 printed circuit board material using ultrashort pulse lasers with emission in the green spectral region. Laser pulse durations in the pico- and femtosecond regime, laser pulse repetition rates up to 400 kHz and laser fluences up to 11.5 J/cm2 are applied to optimize the quality of microvias, as being evaluated by the generated taper, the extension of glass fiber protrusions and damage of inner lying copper layers using materialography.

Ultrashort pulsed laser backside ablation of fused silica.

We report on the fabrication of rectangular microchannels with vertical sidewalls in fused silica by laser backside ablation. A 515 nm femtosecond laser is focused by an objective with a NA of 0.5 through the sample on the glass/air interface, allowing processing from the backside into the bulk material.

Enhanced ablation efficiency using GHz bursts in micromachining fused silica.

We report on micromilling cavities into fused silica by a 1030 nm femtosecond laser using 2.17 GHz bursts. The milled cavities show an increased depth per layer for a higher number of pulses per burst while the ablation efficiency is also increased.

Fabrication and evaluation of negative axicons for ultrashort pulsed laser applications.

We report on the fabrication and evaluation of a sharp tip negative axicon paving the way for applications in high-power ultrashort pulsed laser systems. The negative axicon is manufactured by applying a two-step all laser-based process chain consisting of ultrashort pulsed laser ablation and CO laser polishing finishing the component in less than 5 minutes. The finalized negative axicon reveals a surface roughness of 18 nm, fulfilling optical quality.

Microchannels inside bulk PMMA generated by femtosecond laser using adaptive beam shaping.

In this contribution, we report on the generation of internal microchannels with basically unlimited channel length inside of PMMA bulk material by femtosecond laser. A precisely controllable and stable circular channel cross section is obtained by using a spatial light modulator to compensate the writing depth depending spherical aberration. Furthermore, the generation of a rotatable elliptical input beam by adaptive optics ensures a fitting of the beam shaping to the writing direction.

Laser-fabricated axicons challenging the conventional optics in glass processing applications.

Laser-based fabrication can be an alternative technology to mechanical grinding and polishing processes. However, the performance of these elements in real applications still needs to be validated. In this paper, we demonstrate that the subtractive fabrication technology is able to produce high-quality axicons from fused silica, which can be efficiently used for glass processing.

Fabrication of a high-quality axicon by femtosecond laser ablation and CO laser polishing for quasi-Bessel beam generation.

We report on the fabrication of an axicon by applying a two-step manufacturing process including a 1030 nm femtosecond and a 10.6 µm CO laser. First, the pre-defined axicon geometry is generated by high-precision femtosecond layer-by-layer ablation.