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.

Rapid and high throughput formation of through glass vias

“…A drilling rate of around 1 µm per burst was reported near the surface (to a depth of about 100 µm) and a much slower drill rate of ∼0.2 µm per burst deeper into the material for soda lime glass. 52 For a 1 kHz pulse repetition frequency, which is necessary to minimize thermal effects, this means that a 100 µm deep hole would require about 100 bursts, or 100 ms of drill time and a corresponding throughput of ca. 10 vias per second.…”

Ablation rate assessment of GHz femtosecond laser in burst mode through fast numerical simulation

“…They also reviewed the mechanism involved during ultrashort pulses at GHz regime proposing a first heating phase followed by a self-sustaining ablation mechanism characterized by an almost constant temperature between two pulses. Valuable results were obtained with Gigahertz femtosecond lasers by working on glass [7][8]: Balage et. al.…”

“…al. [7] used a 1030 nm femtosecond laser with an intra-burst pulse repetition rate of 1.28 GHz to obtain high-quality and high-aspect-ratio holes by varying the burst duration and shape, Metzner et al [8], by using an intra-burst rate of 65 MHz and 2.5 GHz, increased the ablation rate at least four times compared to the single pulse mode, while maintaining a comparable surface roughness. In another work, Metzner et al [9] presented deep investigations on ablation and surface quality in stainless steel, cemented tungsten carbide, and silicon irradiated via a 1030 nm laser capable of varying the pulse duration in the range of 270 fs up to 10 ps and generating bursts with an intra-burst pulse repetition rate of 5 GHz.…”

Electro-optic frequency comb generation of 8-GHz repetition-rate and few-picosecond pulse duration at 1-um

“…Recently, the multi-GHz femtosecond pulse burst processing has been compelling in micromachining due to its lower single pulse energy and higher ablated rate [1][2][3]. This pulse burst, including few tens of pulses or more, considered to show different processing mechanism from the conventional single pulse ablation in a few tens of microsecond.…”