## 2 Experimental Methods
### Laser Surface Finishing Process of PCD Workpiece
The workpiece and stage holder can be simultaneously lifted along the Z-axis. As shown in Figure 3a, the starting position of the laser finishing process was set at 48 \(\upmu\)m to the left from the vertical baseline A. The location of baseline A was set at the vertex of the laser-cut upper edge. This starting position was calculated as half the laser spot diameter (18 \(\upmu\)m) plus 6 horizontal shifts (30 \(\upmu\)m). As a result, the laser beam was shifted 6 times to the right and the fringe of the laser focal spot will be in aligned with baseline A. [PERSON] et al. [20] pointed out that as the number of cutting passes increased, the workpiece was cut through and most of the laser energy was no longer focused directly on the side wall of the workpiece; only the fringe of the laser beam (in the vicinity of the laser spot diameter) was focused on the surface of the cut edge. The laser energy density located around the fringe of the laser beam was very low. In this low-fluence regime, the laser intensity was higher than the ablation threshold of the material. The laser beam power was switched from that for laser beam cutting to that for laser beam polishing and had the effect of low-fluence finishing. The flatness of the cut edge and surface roughness were improved. Thus, by referring to the study by [PERSON] et al., the subsequent finishing processes considered multiple passes per path (up to 20 passes) to improve the flatness and surface roughness of the cut PCD surface. (2) Method 2  
The processing paths were similar to those in Method 1. The difference in this method was that it applied 5 passes per path, 80 \(\upmu\)m Z-axis lift, 5 Z-axis lifts (6 layers in total), 10 \(\upmu\)m of horizontal shifting, and 3 horizontal shifts (4 rows in total). (3) Method 3  
The processing paths are plotted as shown in Figure 4. Laser finishing was conducted in the horizontal shifting direction (Layer 1) for 6 shifts (7 rows in total). Then, the stage was lifted in the vertical direction along the Z-axis for processing Layer 2. The finishing was performed with 20 passes per path and horizontal space shift of 5 \(\upmu\)m between paths,  
Figure 3: Laser finishing Method 1: (**a**) The starting position of the laser finishing process (Row 1) was set at 48 \(\upmu\)m to the left from the vertical Baseline A. The vertical direction along the Z-axis of the workpiece was processed first with 20 passes per path. After Layer 1 (Path 1) was processed, the workpiece stage is lifted by 100 \(\upmu\)m in the Z-axis direction to process Layer 2 (Path 2). The total number of Z-axis lifts was 4 (5 paths in total); (**b**) After processing all 5 layers in row 1, the stage was returned to its original position. The focal spot of the laser beam was shifted horizontally by 5 \(\upmu\)m to the right to process the following paths (from Path 6 to Path 10) in Row 2. The processing paths mentioned above were repeated until the number of horizontal shifts reachd6 (7 rows in total). with total number of 6 shifts (7 rows in total). The stage lift in the Z-axis was 100 \(\upmu\)m, and the total number of stage lifts was 4 (5 layers in total).