## 3 Results and Discussion
### SEM Analysis  
SEM micrographs of the CFs before (Figure 6a,b) and after laser irradiation (Figure 6c-p) were acquired in order to observe the differences on the morphology of the exposed surface as a function of different fluences (more detailed SEM micrographs can be found in Section S1). Additional SEM micrographs of PCF UD cloths and TCF rows are provided in Figures S1-S16). Five laser powers were selected (3.75 W, 4.25 W, 4.75 W, 7.5 W, and 10 W), with corresponding fluences of 37 J/cm\({}^{2}\), 42 J/cm\({}^{2}\), 47 J/cm\({}^{2}\), 74 J/cm\({}^{2}\), and 99 J/cm\({}^{2}\), respectively. At the fluence of 37 J/cm\({}^{2}\), there is an insignificant \"roughening\" of the CF surface; however, the presence of small particles was clearly visible when operating the SEM system at 15 kV, indicating that they were quite conductive (Figures 6d and S10). As the fluence was increased to 42 J/cm\({}^{2}\), the density of the particles increased substantially and at  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **Scan Speed (cm/s)** & **Power (W)** & **PPI** & **Fluence (J/cm\({}^{2}\))** \\ \hline TCF\({}_{3.75\,\mathrm{W}}\) & 48.5 & 3.75 & 1000 & 37 \\ \hline TCF\({}_{4.25\,\mathrm{W}}\) & 48.5 & 4.25 & 1000 & 42 \\ \hline TCF\({}_{4.75\,\mathrm{W}}\) & 48.5 & 4.75 & 1000 & 47 \\ \hline TCF\({}_{7.5\,\mathrm{W}}\) & 48.5 & 7.5 & 1000 & 74 \\ \hline TCF\({}_{10\,\mathrm{W}}\) & 48.5 & 10 & 1000 & 99 \\ \hline PCF\({}_{4.25\,\mathrm{W}}\) & 48.5 & 4.25 & 1000 & 42 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Fluence calculation of all irradiated samples.  
Figure 5: (**a**) Fluence, scan speed, and power correlation contour map. (**b**) Relationship between fluence and scan speed at different laser beam powers.  
47 J/cm\({}^{2}\) the \"roughening\" of the CF surface became apparent (Figures 6f,h, S11 and S12), through the development of nanosized \"vertical fins.\" When the fluence surpassed the value of \(\sim\)50 J/cm\({}^{2}\), CF destruction was observed (fibers were cut) (Figure 6i-l). A closer look at the destructed area revealed the formation of 200-300 nm cauliflower-liked graphitic structures (Figures 6j,l, S13 and S14--green dashed circular areas), indicating that an engraving phenomenon took place prior to the cutting, creating significant modulations on the CFs. In addition, Figures 6l and S14 reveal the removal of skin layers from the surface of the fiber (blue highlighted dashed area), suggesting that the laser beam actually etched the CFs' surface layer by layer.  
The fluences of the experimental work in this paper were selected below the threshold value of 50 J/cm\({}^{2}\), where no broken fibers were detected. However, at the fluence of 47 J/cm\({}^{2}\) a noticeable expansion on the CFs' diameter was noted, which was an indication for the thermal loading within the bulk of the fiber. It is worth noting that due to the non-uniform flatness of a woven carbon cloth (e.g., warp and weft directions have different heights) the focal spot size was varying generating substantial heterogeneity on the irradiated areas. In order to assure the uniformity of the irradiated area a Unidirectional (PCF) cloth was selected (Figures 6m-p, S1-S7, S15, and S16) for Mode-I experiments (more SEM micrographs of PCF samples can be found in the supporting information, Section S1, Figures S1-S7).