Plasma dynamics and structural modifications induced by femtosecond laser pulses in quartz

• Published in: Applied surface science 2012-09, Vol.258 (23), p.9389-9393
• Main Authors: Hernandez-Rueda, J., Puerto, D., Siegel, J., Galvan-Sosa, M., Solis, J.
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Dynamics; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; Femtosecond laser; Fused silica; Impact phenomena (including electron spectra and sputtering); Laser-beam impact phenomena; Microscopy; Physics; Plasma; Pump-probe; Quartz
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2011.12.020

► Irradiation of quartz with single fs laser pulses at increasing pulse energies. ► Ablation at high local fluences and surface depression at low fluences. ► Fs-microscopy shows that free electron plasma causes surface depression. ► Surface depression is consistent with an increased material density. ► Low steady-sate reflectivity indicates creation of defects. We have investigated plasma formation and relaxation dynamics induced by single femtosecond laser pulses at the surface of crystalline SiO2 (quartz) along with the corresponding topography modifications. The use of fs-resolved pump-probe microscopy allows combining spatial and temporal resolution and simultaneous access to phenomena occurring in adjacent regions excited with different local fluences. The results show the formation of a transient free-electron plasma ring surrounding the location of the inner ablation crater. Optical microscopy measurements reveal a 30% reflectivity decrease in this region, consistent with local amorphization. The accompanying weak depression of ≈15nm in this region is explained by gentle material removal via Coulomb explosion. Finally, we discuss the timescales of the plasma dynamics and its role in the modifications produced, by comparing the results with previous studies obtained in amorphous SiO2 (fused silica). For this purpose, we have conceived a new representation concept of time-resolved microscopy image stacks in a single graph, which allows visualizing quickly suble differences of the overall similar dynamic response of both materials.