## 3 Results  
### Plume Images  
Figure 5 shows the dynamic plume images of three carbon-doped composite propellants and pure PTFE. The plume evolution of the nano-carbon-doped composite propellant is shown in Figure 5a. When the laser was applied to the sample, it immediately generated a bright, rounded plume cluster on the ablation surface. As the ablation continued, this rounded plume cluster expanded and eventually split at ~300 us, forming a jet and a large tail plume cluster emanating from the surface. However, the distribution of the jet and the plume cluster at the tail end was not uniform, and noticeable fractures were observed. Additionally, the tail plume cluster appeared dim and deflected downwards. At the end of a laser pulse, the jet gradually disappeared, while the tail plume cluster expanded and eventually dissipated.  
Figure 5: Plume images of different propellant formulas.  
Figure 5b shows the plume evolution of the graphite-doped composite propellant. Similar to the previous case, when the sample was subjected to laser ablation, a bright rounded plume cluster appeared on the ablation surface, expanding continuously. The difference was that this cluster split both upwards and downwards at \(\sim\)600 \(\upmu\)s, forming a larger plume cluster with relatively lower brightness. Simultaneously, a bright jet was generated on the ablation surface, with noticeable splash particles observed around it. As the ablation progressed, both the jet and large plume cluster spread outwards gradually, with the tail jet and plume cluster deflected upwards. The brightness at the tail end of the jet was unevenly distributed, but there were no observed fractures during the ablation. At the end of a laser pulse, the jet did not disappear immediately but slowly darkened until it vanished. The residual plume cluster continued to spread until it completely dissipated.  
The plume evolution of the graphene-doped composite propellant is shown in Figure 5c. When the laser was irradiated at the propellant sample, a bright rounded plume cluster rapidly formed on the ablation surface, expanding continuously. However, this rounded plume cluster started to split at \(\sim\)100 \(\upmu\)s and deflect downwards. Similar to the previous two cases, the jet of the sample originated from the ablation surface, but its tail exhibited less uniformity with lower brightness. Nevertheless, the overall brightness level was higher than that of the former two cases. The tail plume cluster expanded throughout the ablation process, primarily distributed below the jet during the early stage and above the jet at the later stage of ablation. Bright particles were observed around the jet, including its tail. Additionally, a noticeable fracture appeared at the tail end of the jet during the late stage of ablation.  
Figure 5d shows the plume evolution of the pure PTFE sample, it can be observed that the plume generated by laser ablation of PTFE was less pronounced when compared to composite propellants fabricated of PTFE filled with nano-carbon, graphite, and graphene, indicating that the presence of these carbon particles enhanced the interaction between the laser and the propellant due to their higher optical absorption coefficient compared to that of PTFE.