## 3 Results and Discussion
### Influence of Processing Point Spacing on Cutting Quality  
The cutting results of different processing point spacing are shown in Figure 4 with a 100 kHz pulse-repetition frequency. The laser incidence at the morphology of a straight line of micropores was melt sputtering; when the processing point spacing was 1 um, as shown in Figure 4a, micropores were connected to form an ablation groove. When the processing point spacing was more than 2 um, the micropores were separated. When the processing point spacing was 4 um, the micropores were more widely spaced, and cracks formed around the micropores. The microporous area is shown in Figure 4d. Figure 4: Diagrams of the samples with different processing point spacings and local SEM scans at a laser re-frequency of 100 kHz, an incident laser power of 11.5 W, and burst mode of 2. (**a**–**d**) represent the cross-section and the upper surface of the samples with processing point spacing of 1–4 μm, respectively, and (**e**,**f**) represent the SEM schemes of the edges of the modified layer at the processing point spacing of 4 μm. The cross-section roughness increased with the increase in the machining point spacing, and the uniformity of ablation further decreased when the point spacing was 3 \(\upmu\)m versus 4 \(\upmu\)m and above. The unaltered region increased with the machining spacing of 4 \(\upmu\)m, which made the sample separation difficult. As shown in Figure 4d under the magnification of 1.83 k and Figure 4e under the magnification of 6.49 k in the SEM picture, a series of intermittent laser ablation cavities could be observed in the cross-section of soda-time glass. Further, a series of cavities constituted the nanochannels, with ablation diameters of about 690 nm, and the area between the nanochannels was obviously insufficient for modification. Similar nanochannels were also found at point spacings less than 4 \(\upmu\)m. Still, the distance between submicron channels decreased when the processing point spacing was too small to improve the observation difficulty. When the point spacing was 1 \(\upmu\)m, the affected areas of submicron channels overlapped, and no obvious channel morphology could be observed. Roughness characterization of the sample cross-sections produced by different machining point spacings are shown in the results in Figure 5a below, where the roughness increases with increasing machining point spacing, with a relatively large roughness in the region of the sample near the middle, which was in line with the trend of the Bessel beam energy with the \(Z\)-axis used in this experiment. When the point spacing was 1 \(\upmu\)m, the roughness difference between the regions was not obvious, and as the point spacing increased, the regions of the sample cross-section showed different modified morphology, and the difference in roughness between the regions became larger. The difference in average roughness between regions 2 and 3 reached 157 nm at 4 \(\upmu\)m.  
In summary, the optimal processing quality was achieved when the processing point spacing was 1 \(\upmu\)m and the overall modification was uniform. Samples with different processing point spacings were tested in terms of breaking strength using a hand-pressure mechanical testing system, and the variation in stress with laser processing point spacing is shown in Figure 5b. The increase in point spacing led to a similar increase in the unmodified region, and the required stress in the samples increased due to the increase in the unmodified region. Combined with Figure 4, it can be seen that the point spacing increases, the submicron channel spacing increases, the unmodified area between the channels increases, and the influence of the lobes increases, which is the main reason for the increase in sample roughness. Roughness and breaking strength followed the same trend as the point spacing variation. Figure 5: **(a)** Scheme of variation in cross-section roughness with processing point spacing with an incident laser power of 11.5 W and burst mode of 2.