Advances in Femtosecond Laser GHz-Burst Drilling of Glasses: Influence of Burst Shape and Duration

Abstract

The femtosecond GHz-burst mode laser processing has attracted much attention in the last few years. Very recently, the first percussion drilling results obtained in glasses using this new regime were reported. In this study, we present our latest results on top-down drilling in glasses, focusing specifically on the influence of burst duration and shape on the hole drilling rate and the quality of the drilled holes, wherein holes of very high quality with a smooth and glossy inner surface can be obtained. We show that a decreasing energy repartition of the pulses within the burst can increase the drilling rate, but the holes saturate at lower depths and present lower quality than holes drilled with an increasing or flat energy distribution. Moreover, we give an insight into the phenomena that may occur during drilling as a function of the burst shape.

Keywords: femtosecond GHz-bursts; glasses; laser–material interaction; percussion drilling; ultrafast laser processing.

Figure 1

Schematic representation and measured shape of a classical burst (a,b), of a decreasing burst (c,d), of an increasing burst (e,f), and of a flat burst (g,h).

Figure 2

Blueprint of the experimental setup used for the drilling experiments.

Figure 3

Microscope images of the holes drilled with a classical burst shape and a burst energy of 172 µJ in sodalime for 300 bursts, 400 bursts, and 500 bursts with 36 ppb (a), 70 ppb (b), 100 ppb (c) and 130 ppb (d), and for fused silica for bursts of 36 ppb (e), 70 ppb (f), 100 ppb (g) and 130 ppb (h).

Figure 4

Evolution of the hole depth as a function of the number of bursts up to 10,000 bursts of 172 µJ burst energy for sodalime (a) and fused silica (b). The inserts on the right bottom corner are a zoom of the very first part of the graphs delimited by a rectangle of black dashed lines.

Figure 5

Microscope images of the holes drilled in sodalime with 100-pulse GHz-bursts of 200 µJ, with a number of bursts in a range from 200 to 800 for a decreasing burst shape (a), for an increasing burst shape (b) and for a flat burst shape (c).

Figure 6

Evolution of the hole depth in sodalime as a function of the number of bursts applied on the sample for the three burst shapes, with bursts of 100 pulses and a burst energy of 200 µJ.

Figure 7

Microscope image of the holes drilled in sodalime for a drilling time of 1 s, with bursts of 100 pulses at a burst energy of 200 µJ, and a decreasing burst shape (a), an increasing burst shape (b), and a flat burst shape (c).