Fig. 1. Schematic representation of the nanosecond and picosecond laser damage tests performed on three types of MLDG samples: (a) unconditioned MLDG, (b) MLDF conditioning and (c) MLDG conditioning. (d) Schematic of the raster scan damage tests.

Fig. 2. OM images of the nodular ejection pits and plasma scalds originating from Protocol 1. (a), (b) Before photoresist spin-coating after MLDF conditioning. (c), (d) After photoresist spin-coating. (e), (f) After MLDG cleaning.

Fig. 3. SEM images of the nodular defect and ejection pits at the different MLDG fabrication stages. (a) Typical bulged nodular defect in the MLDF and (b)–(d) morphologies of the nodular ejection pits after the MLDF conditioning, photoresist spin-coating and grating cleaning, respectively.

Fig. 4. (a) Typical cross-sectional morphology of a nodular defect in the unconditioned MLDG. (b), (c) SEM images of the typical nodular ejection pits caused by Protocols 1 and 2, respectively. (d)–(f) Simulated distributions corresponding to the morphological structures in (a)–(c), respectively.

Fig. 5. (a) SEM image of the plasma-scalding region induced by the NLC in Protocol 1; the inset image shows a local magnified view of the nodular ejection pit. (b)−(g) Local magnified SEM images of the positions marked by rectangles (in color) in (a).

Fig. 6. (a) SEM image of the plasma-scalding region induced by the NLC in Protocol 2; the inset image indicates the local magnified view of the central nodular ejection pit. (b)−(g) Local magnified SEM images of the positions marked by rectangles (in color) in (a).

Fig. 7. (a) LIDT results of the nanosecond laser raster scan; the two thresholds represent the results of two different test samples. (b) Damage density versus laser fluence (only the damage points that appear in the nanosecond laser damage test process are counted as damage).

Fig. 8. (a) OM image showing the pristine morphological modifications of the three nodular ejection pits induced by the NLC in Protocol 1. (b)–(f) OM images showing the morphologies of the ejection pit areas irradiated by gradually increasing nanosecond laser fluences; here, the red lines represent the nodular ejection pits on the MLDG.

Fig. 9. (a) OM image showing the pristine morphological modifications of a nodular ejection pit induced by the NLC in Protocol 2. (b)–(f) Ejection pit region irradiated by gradually increasing nanosecond laser fluences.

Fig. 10. Picosecond-LIDTs of the unconditioned nodule and nodular ejection pits conditioned by Protocols 1 and 2.

Fig. 11. Typical morphological characteristics of the different test areas induced during the picosecond laser damage test. (a), (d) Unconditioned nodular defects. (b), (e) Nodular ejection pits caused by Protocol 1. (c), (f) Nodular ejection pits caused by Protocol 2 (where F denotes the incident laser fluence).

Fig. 12. (a) OM image showing the pristine morphological modification of a nodular ejection pit in Protocol 1. (b)–(f) OM images showing the morphologies of the ejection pit area irradiated by the gradually increasing picosecond laser fluences.

Fig. 13. (a) OM image showing the pristine morphological modification of a nodular ejection pit in Protocol 2. (b)–(f) OM images showing the morphologies of the ejection pit area irradiated by the gradually increasing picosecond laser fluences.