Fig. 1. Schematic diagram of experimental setup for laser damage test

Fig. 2. Damage morphologies of CaF₂ crystals under different pulse numbers

Fig. 3. Relationship between diameter of damage site and pulse number in CaF₂ crystals

Fig. 4. Calculated damage threshold results under different diameter selection methods. (a) Different diameter selection methods;

Fig. 5. Schematic diagram of damage by laser direct writing

Fig. 6. Morphologies of damage lines in CaF₂ crystals at different direct writing speeds. (a) 5 μm/s; (b) 10 μm/s; (c) 20 μm/s; (d) 40 μm/s; (e) 60 μm/s; (f) 100 μm/s; (g) 200 μm/s

Fig. 7. Test results of CaF₂ crystal damage line. (a) Cross section of CaF₂ crystal damage line; (b) AFM scan result of CaF₂ crystal damage line

Fig. 8. Relationship between CaF₂ crystal damage line width and direct writing speed

Fig. 9. Fitting result of direct writing damage threshold in CaF₂ crystals