Film-substrate’s interfacial bonding strength is closely related to film quality. An excellent interfacial bonding strength is the premise for the well use of film. The laser detecting technique of discrete scratches...Film-substrate’s interfacial bonding strength is closely related to film quality. An excellent interfacial bonding strength is the premise for the well use of film. The laser detecting technique of discrete scratches based on laser shockwave effect is a new method, which can measure interfacial bonding strength. With this technique, film-substrate system is of transient load of different laser energy, the relation between the dynamic response characteristics of such film-substrate system and film-substrate’s interfacial bonding strength is a core problem to be solved urgently. On this basis, this paper conducted research on the dynamic response characteristics of film-substrate system during laser loading process using detecting technique of PVDF patch sensor. Results show that under the irradiation of different laser energy, it can detect dynamic responses of theory models of different film-substrate system using PVDF patch sensor, wherein shockwave dynamic response and dynamic strain response are included. Laser energy and interfacial bonding strength are of a regular influence to the dynamic response of film-substrate system theory model.展开更多
The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during t...The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during the second pulse irradiation on the crater induced by the first pulse, the expansion of the plasma and shockwave is enhanced in the longitudinal direction. The plasma model and Fresnel diffraction theory are combined to calculate the laser intensity distribution by considering the change in surface morphology and transient material properties. The theoretical results show that after the free electron density induced by the rising edge of the pulse reaches the critical density, the originally transparent surface is transformed into a transient high-reflectivity surface(metallic state). Thus, the crater with a concave-lens-like morphology can tremendously reflect and refocus the latter part of the laser pulse, leading to a strong laser field with an intensity even higher than the incident intensity. This strong refocused laser pulse results in a stronger laser-induced air breakdown and enhances the subsequent expansion of the plasma and shockwave. In addition, similar shadowgraphs are also recorded in the single-pulse ablation of a concave microlens, providing experimental evidence for the enhancement mechanism.展开更多
文摘Film-substrate’s interfacial bonding strength is closely related to film quality. An excellent interfacial bonding strength is the premise for the well use of film. The laser detecting technique of discrete scratches based on laser shockwave effect is a new method, which can measure interfacial bonding strength. With this technique, film-substrate system is of transient load of different laser energy, the relation between the dynamic response characteristics of such film-substrate system and film-substrate’s interfacial bonding strength is a core problem to be solved urgently. On this basis, this paper conducted research on the dynamic response characteristics of film-substrate system during laser loading process using detecting technique of PVDF patch sensor. Results show that under the irradiation of different laser energy, it can detect dynamic responses of theory models of different film-substrate system using PVDF patch sensor, wherein shockwave dynamic response and dynamic strain response are included. Laser energy and interfacial bonding strength are of a regular influence to the dynamic response of film-substrate system theory model.
基金National Natural Science Foundation of China(NSFC)(51605029,91323301)
文摘The dynamics of plasma and shockwave expansion during two femtosecond laser pulse ablation of fused silica are studied using a time-resolved shadowgraph imaging technique. The experimental results reveal that during the second pulse irradiation on the crater induced by the first pulse, the expansion of the plasma and shockwave is enhanced in the longitudinal direction. The plasma model and Fresnel diffraction theory are combined to calculate the laser intensity distribution by considering the change in surface morphology and transient material properties. The theoretical results show that after the free electron density induced by the rising edge of the pulse reaches the critical density, the originally transparent surface is transformed into a transient high-reflectivity surface(metallic state). Thus, the crater with a concave-lens-like morphology can tremendously reflect and refocus the latter part of the laser pulse, leading to a strong laser field with an intensity even higher than the incident intensity. This strong refocused laser pulse results in a stronger laser-induced air breakdown and enhances the subsequent expansion of the plasma and shockwave. In addition, similar shadowgraphs are also recorded in the single-pulse ablation of a concave microlens, providing experimental evidence for the enhancement mechanism.
