<title>Laser micromachining of transparent fused silica with 1-ps pulses and pulse trains</title>

Abstract

Ablation rates and etched-surface morphology of fused silica has been studied with i-ps Nd:giass laser pulses in a regime of near-diffraction-limited spot size. Shallow holes of 1.7-tim diameter were too small for the formation of laser-induced periodic-surface structures. Atomic-force and scanning-electron microscopy showed that reproducible etch depth and moderately smooth surfaces are attainable for low fluences of 5.5 -45 J/cm2 -the "gentle" ablation regime. Etch depth progressed linearly with the number of laser pulses until the onset of surface swelling and shock-induced microcracks after a critical number N of laser pulses, scaling as N i.7 +80/F (fluence F in J/cm2). Below this limit -for accumulated etch depths less than -2 m -three-dimensional surface structuring with sub-micron precision is possible with picosecond-laser pulses. In the strong ablation regime (F > 45 J/cm2), surface morphology was poor and microcracking developed within 2-4 pulses. These shock-induced microcracking effects were eliminated when a mode-locked train of -400 identical i-ps pulses, each separated by 7.5 ns, was applied. Very smooth and deep (-30-im) holes of 7-10-.tm diameter were excised at a total fluence of -400 kJ/cm2, establishing a new means for rapid and precise micromachining of fused silica and other brittle materials.

Femtosecond Laser 3D Fabrication in Porous Glass for Micro- and Nanofluidic Applications

“…The significant amount of heat and strong shock waves generated by the femtosecond laser ablation can facilitate water circulation and help to remove the debris from the outlet of the microchannel. Since the high-repetition-rate laser pulses could also lead to temporary evacuation of water in the laser action zone by semi-continuous irradiation, a chopper operated at 1 kHz with a duty of 50/50 was used (see Figure 1) to modulate the femtosecond laser pulse train during the ablation process, so that the water can always fill the ablation zone by infiltration through the mesoporous network [47].…”

Engineering meter-scale laser resistant coatings for the near IR

“…The three most promising techniques are exposure to a CO 2 laser, 25 micro-machining using a high-speed air turbine equipped with a very small single-crystal diamond bit, 26 and laser ablation by a short pulse laser. 27 All of these concepts are a means of removing laser damage and leaving a smooth fracture-free pit that is laser resistant. Each of these processes were also explored for mitigation of damage on high reflector coatings, although there was no significant process optimization specific to optical coatings.…”

Pulsetrain-burst mode, ultrafast-laser interactions with 3D viable cell cultures as a model for soft biological tissues

“…It has been shown in materials science applications that changing either the pulsetrain-burst duration, spacing between pulses, and/or pulse intensity can control melting in glass [19][20][21] and dental hard tissue [22]. Pulsetrain-burst delivery is also characteristic of free-electron lasers (FELs) [23][24][25], which typically generate a burst of picosecond pulses at very high repetition rates (> 1 GHz) within a macropulse of some microseconds duration.…”