Fig. 1. Schematic diagram of femtosecond filament principle

Fig. 2. Schematic diagram of laser processing system

Fig. 3. Schematic diagrams of laser filament processing. (a) Laser filament focusing; (b) scribe-cutting; (c) ring-cutting of microporous

Fig. 4. Influence of laser focusing position on processing morphology. (a) Schematic diagram of processing with different laser focusing positions; (b) relationship between damage depth and focusing position; (c) damage morphology

Fig. 5. Quartz glass morphology with increasing pulse energy at different laser frequencies. (a) 50 kHz; (b) 100 kHz; (c) 200 kHz; (d) surface morphology after cleaning; (e) cross-section of uncleaned optical filament damage

Fig. 6. Variation of damage depth and width with pulse energy at different laser frequencies. (a) Damage depth; (b) damage width

Fig. 7. Schematic of laser spot overlap

Fig. 8. Cross-sectional morphology of filament damage with different scanning speeds

Fig. 9. Laser processing topographic map with scanning number (n) from 1 to 10

Fig. 10. Cut section morphology of quartz glass. (a) Laser filament processing method; (b) progressive scanning method

Fig. 11. Processing morphology of quartz glass microporous. (a) Laser filament processing method; (b) conventional progressive scanning method