Percussion drilling in glasses and process dynamics with femtosecond laser GHz-bursts.

We report for the first time to our knowledge on top-down percussion drilling of high-quality deep holes in different glasses with femtosecond laser pulses in GHz-burst mode. We reveal the dynamics of the percussion drilling process by pump-probe shadowgraphy and thermal camera imaging demonstrating that the drilling process in GHz-burst mode is fundamentally different from single-pulse processing and confirming the presence of thermal accumulation. Moreover, we show a comparison to drilling by femtosecond single-pulses containing an equal laser fluence in sodalime, alkali-free alumina-borosilicate, fused silica, and sapphire.

Systematic study of laser ablation with GHz bursts of femtosecond pulses.

We report on crater formation, line scribing and cavity milling experiments on Silicon, Copper, Aluminum and stainless steel with GHz bursts of femtosecond pulses. The intra-burst repetition rate has been varied between 0.88 and 3.

High-efficiency femtosecond ablation of silicon with GHz repetition rate laser source.

We report on silicon ablation with a 20 W GHz amplified femtosecond laser source. This novel laser delivers burst energies up to 400 μJ, providing flexible intra-pulse repetition rates of 0.88 or 3.

Multiscale grooved titanium processed with femtosecond laser influences mesenchymal stem cell morphology, adhesion, and matrix organization.

The femtosecond laser processing enabled the structuring of six types of surfaces on titanium-6aluminium-4vanadium (Ti-6Al-4V) plates. The obtained hierarchical features consisted of a combination of microgrooves and oriented nanostructures. By adjusting beam properties such as laser polarization, the width of the microgrooves (20 or 60 μm) and the orientation of the nanostructures (parallel or perpendicular to the microgrooves) can be precisely controlled.

Electrochemical boron-doped diamond film microcells micromachined with femtosecond laser: application to the determination of water framework directive metals.

Planar electrochemical microcells were micromachined in a microcrystalline boron-doped diamond (BDD) thin layer using a femtosecond laser. The electrochemical performances of the new laser-machined BDD microcell were assessed by differential pulse anodic stripping voltammetry (DPASV) determinations, at the nanomolar level, of the four heavy metal ions of the European Water Framework Directive (WFD): Cd(II), Ni(II), Pb(II), Hg(II). The results are compared with those of previously published BDD electrodes.

Time-resolved imaging of laser-induced refractive index changes in transparent media.

We describe a method to visualize ultrafast laser-induced refractive index changes in transparent materials with a 310 fs impulse response and a submicrometer spatial resolution. The temporal profile of the laser excitation sequence can be arbitrarily set on the subpicosecond and picosecond time scales with a pulse shaping unit, allowing for complex laser excitation. Time-resolved phase contrast microscopy reveals the real part of the refractive index change and complementary time-resolved optical transmission microscopy measurements give access to the imaginary part of the refractive index in the irradiated region.

Periodic nanoscale structures on polyimide surfaces generated by temporally tailored femtosecond laser pulses.

A strong influence of different pulse durations and double pulse delay times on the formation of periodic surface structures on polyimide were observed employing ultrashort laser pulses tailored on a sub-picosecond and picosecond time scale. Multi-photon, defect-related excitation mechanisms and thermal expansion of the polymer lattice correlated to a loss of long range order and polarisation memory were considered.

10 kHz water-cooled Ti :Sapphire femtosecond laser.

We demonstrate operation of a simple and reliable water-cooled femtosecond laser running at 10 kHz suitable for industrial micromachining applications. A laser geometry involving only a regenerative amplifier and delivering 3.5 W average power 60-fs pulses is compared to a more conventional architecture using an additional multi-pass amplifier.

Programmable focal spot shaping of amplified femtosecond laser pulses.

We describe the programmable spatial beam shaping of 100-kHz, 4-microJ amplified femtosecond pulses in a focal plane by wave-front modulation. Phase distributions are determined by a numerical iterative procedure. A nonpixelated optically addressed liquid-crystal light valve is used as a programmable wave-front tailoring device.