Ultrafast nanoporous silica formation driven by femtosecond laser irradiation
Ultrafast nanoporous silica formation driven by femtosecond laser irradiation
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DOI：
10.1002/lpor.201300043
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发表时间：
2013-11-01
影响因子：
11
通讯作者：
Brisset, Francois
中科院分区：
文献类型：
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作者：
Lancry, Matthieu;Poumellec, Bertrand;Brisset, Francois
在飞秒激光照射后发生的一种类型的玻璃改性引起强（10（-2））双折射。这种形式的双折射被认为与折射率纳米结构（称为纳米光栅）有关。使用具有nm分辨率的扫描电子显微镜（SEM）分析熔融二氧化硅中的诱导轨道表明，纳米结构是平均折射率低于典型二氧化硅（n近似为-0.20）的多孔纳米平面。它们的起源被解释为产生于本地化的，高强度的飞秒激光辐射下的玻璃的快速分解，其中强非线性，多光子诱导的光电离导致等离子体的产生。机制的细节包括库仑爆炸的特点，强烈的光电离和生产的自陷激子（STE）。这些STE的快速弛豫防止了复合，并且离解的原子氧相反地彼此复合以形成使用拉曼显微镜指出的分子氧。其中一些溶解在凝聚的玻璃中，而其余的则被困在纳米空隙中。化学复合只能在1200摄氏度下发生数小时。这解释了这种纳米结构的热稳定性。这些双折射纳米多孔结构的精确激光平移和控制允许在玻璃内任意调谐和定位，这是控制光子应用、催化剂、分子筛、复合材料等的光学性质的重要工具。
A type of glass modifications occurring after femto-second laser irradiation gives rise to strong (10(-2)) from birefringence. This form birefringence is thought to be related to index nanostructure (called nanogratings). Analyzing induced tracks in fused silica using scanning electron microscopy (SEM) with nm resolution shows that nanostructures are porous nanoplanes with an average index lower than typical silica (n approximate to -0.20). Their origin is explained as arising from fast decomposition of the glass under localized, high-intensity femtosecond laser radiation where strong nonlinear, multiphoton-induced photoionization leads to plasma generation. Mechanistic details include Coulombic explosions characteristic of strong photoionization and the production of self-trapped exciton (STE). Rapid relaxation of these STE prevents recombination and dissociated atomic oxygen instead recombines with each other to form molecular oxygen pointed out using Raman microscopy. Some of it is dissolved in the condensed glass whilst the rest is trapped within nanovoids. A chemical recombination can only occur at 1200 degrees C for many hours. This explains the thermal stability of such a nanostructure. Precise laser translation and control of these birefringent nanoporous structures allo arbitrarily tuning and positioning within the glass, an important tool for controlling optical properties for photonic applications, catalysts, molecular sieves, composites and more.