# Gorilla Glass Cutting Using Femtosecond Laser Pulse Filaments
## 1 Introduction
As compared to CO\({}_{2}\) lasers, nanosecond lasers produce a smaller heat-affected zone near the edges of the cut and thus require minimal post processing. Nanosecond laser cutting technology is relatively fast, which makes it suitable for high throughput and mass production. However, during nanosecond laser-based glass cutting, debris are evident around the cutting area that may create health hazards. In contrast, the heat affected zone should be removed during display glass processing. Improvements in edge quality and heat affected zones were achieved using picosecond laser-based glass cutting technology [19; 20; 21; 22; 23]. Picosecond lasers deliver ultra-short pulses allowing high precision cuts in glasses. The heat affected zone is also minimized, which reduces the possibility of cracking, chipping, or any other kinds of damage to the surrounding glass. Picosecond lasers also operate at high speeds and are thus suitable for high throughput. Despite the high precision, picosecond lasers can still produce micro-cracks in some glass substrates. Additionally, little debris was evident near the cut area during picosecond laser assisted glass cutting. To overcome the limitations of nanosecond and picosecond laser-based glass cutting techniques, researchers considered femtosecond laser-based technology for cutting large variety of glass substrates [24; 25; 26]. Femtosecond lasers offer high precision, negligible heat affected zone, and debris free cut. In addition, femtosecond lasers ensure high quality finishing and clean cuts without forming burrs or micro-cracks. However, the processing time of femtosecond laser-based glass cutting is relatively high compared to other laser based technologies. Currently, femtosecond lasers with a pulse repetition rate of several MHz are commercially available to overcome the throughput problem of the technology. The thickness of the glasses is limited in most of the laser-assisted glass cutting technologies. This problem can be overcome by means of femtosecond laser pulse filaments [27; 28; 29; 30; 31; 32; 33; 34; 35]. Femtosecond laser pulse filaments are evident when a high-intensity femtosecond laser beam propagates through glass materials. When the laser pulse intensity is high enough to cross the critical power required for self-focusing, the laser pulses form a self-sustained and narrow high-intensity channel, known as filaments [27; 28; 29; 30; 31; 32; 33; 34; 35]. [PERSON] and his research group demonstrated the distribution of fringe-type filaments present in high-intensity femtosecond laser beam and controlling mechanism of filaments orientation and number by means of beam shapers [27]. Several research groups proposed the formation of femtosecond laser single pulse filament-assisted high aspect ratio micro-void inside fused silica glass [28; 29] and BK7 glass [30]. Researchers reported the formation of periodic high aspect ratio micro-voids inside fused silica glass by means of periodic femtosecond laser pulse filaments arrays [32; 33]. Another research group fabricated long micro-voids inside BK7 glass using burst-train filaments [35]. In one of our research works, we formed periodic high aspect ratio micro-holes array inside boro-aluminosilicate glass using periodic femtosecond laser pulse filaments [36]. [PERSON] and his research group are pioneers in utilizing periodic femtosecond laser pulse filaments to cut display glass samples (Corning Eagle 2000). The highest length of the filament was \(\sim\)75 \(\upmu\)m. Glass cutting was achieved by fabricating periodic voids' array in several layers inside the sample glasses followed by mechanical pressure [37]. Although the technology is simple, it requires multi-layer void fabrication that increases processing time. In addition, the distance among the layers should be properly calculated before fabrication. The same research group proposed display glass cutting using single layer periodic voids' array formed by femtosecond laser pulse filaments.