Silica ablation process induced by focused laser plasma soft x-rays

Tetsuya Makimura; Shuichi Torii; Hiroyuki Niino; Kouichi Murakami

doi:10.1117/12.911978

12 January 2012 Silica ablation process induced by focused laser plasma soft x-rays

Tetsuya Makimura, Shuichi Torii, Hiroyuki Niino, Kouichi Murakami

Proceedings Volume 8206, Pacific Rim Laser Damage 2011: Optical Materials for High Power Lasers; 82061D (2012) https://doi.org/10.1117/12.911978
Event: Pacific Rim Laser Damage Symposium: Optical Materials for High Power Lasers, 2011, Shanghai, China

Abstract

We have investigated ablation process of silica glass induced by X-ray irradiation. X-rays around 100 eV were generated by irradiation of Ta targets with Nd:YAG laser light. The laser plasma soft X-rays have a pulse duration of 10 ns. The soft X-rays were focused on silica surfaces at up to 10⁸ W/cm². We found that silica glass can be ablated by X-ray irradiation. Typically, the ablated surface have a roughness of 1 nm after ablation by 500 nm in depth. Further, trenches with a width of 50 nm can be clearly fabricated on silica surface. Thus, high quality, practical micromachining can be achieved by the X-ray technique. It is remarkable that more precise features can be fabricated on silica surface than the thermal diffusion length. The results implies non-thermal ablation process. We observed ions ejected from silica surfaces during the irradiation and found that ions are almost atomic species such as Si⁺, O⁺, Si₂⁺, O₂⁺, SiO⁺. The results revealed that silica surfaces are broken into atomic species by X-ray irradiation. Among X-ray ablated species, 0.5-15 % are estimated to be ionized. Even though 0.5 % atoms are ionized in silica surface, the energy density of Coulomb repulsive force is higher than the energy density of binding energy of silica glass. Therefore, we can conclude that Coulomb repulsion between X-ray generated ions are essential for X-ray ablation of silica glass.

Citation Download Citation

Tetsuya Makimura, Shuichi Torii, Hiroyuki Niino, and Kouichi Murakami "Silica ablation process induced by focused laser plasma soft x-rays", Proc. SPIE 8206, Pacific Rim Laser Damage 2011: Optical Materials for High Power Lasers, 82061D (12 January 2012); https://doi.org/10.1117/12.911978

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