Observation of Species Ablated from Fused Silica by F2-KrF Multiwavelength Excitation Process

Dynamics of ablation of fused silica by multiwavelength excitation process using F₂ and KrF excimer laser has been investigated by energy analyzed mass spectrometry of ablated species. The number of generated Si⁺ ion by multiwavelength excitation process corresponds to that by single-F₂ laser ablation and to approximately 2.1 times higher than that by single-KrF excimer laser ablation. In addition, kinetic energy distribution of Si⁺ ablated by multiwavelength excitation process shows almost same as that by single-F₂ laser ablation. We regard that absorption of KrF excimer laser by excited state generated by F₂ laser (excited-state absorption: ESA) causes effective photoionization, resulting in enhancement of Si⁺ with higher kinetic energy and then in high-quality ablation.