AI 中文总结
本研究采用TDDFT第一性原理模拟，揭示TiO₂在10¹³ W/cm²激光强度下的非线性光学响应，对比其不同晶相的光学特性，为高功率介质镜应用提供微观光学退化机制的见解。
AI 中文摘要
介质多层镜是高功率激光光学实验中的核心组件，二氧化钛（TiO₂）作为高折射率介质材料被广泛应用。本研究基于含时密度泛函理论（TDDFT），采用实时第一性原理电子动力学模拟，探究TiO₂在强超短激光脉冲作用下的非线性光学响应。研究揭示了由多光子激发和光激发自由载流子驱动的强度依赖吸收，并采用多尺度Maxwell-TDDFT框架模拟TiO₂纳米薄膜中电子-光耦合动力学。通过直接评估反射场与透射场，发现高功率密度（I~10¹³ W/cm²）下TiO₂的反射率降低，表现出显著的非线性光学响应。此外，本研究对比了TiO₂的多种稳定及亚稳态晶相——金红石、锐钛矿、板钛矿、TiO₂-II和TiO₂-B，以及非超胞模型的光学响应特性。上述结果为暴露于强飞秒激光场的TiO₂基介质光学组件的强度依赖光学退化提供了微观层面的理解。
英文摘要
Dielectric multilayer mirrors are essential components in optical experiments using high-power lasers, where titanium dioxide (TiO$_2$) is widely employed as a high-refractive-index dielectric material. In this study, we investigate the nonlinear optical response of TiO$_2$ under intense ultrashort laser pulses using real-time first-principles electron-dynamics simulations based on time-dependent density functional theory (TDDFT). We reveal intensity-dependent absorption driven by multiphoton excitation and optically excited free carriers, and simulate the resulting electron-light coupled dynamics in TiO$_2$ nanofilms using a multiscale Maxwell-TDDFT framework. Direct evaluation of the reflected and transmitted fields shows reduced reflectance at high intensities ($I \sim 10^{13}$ W/cm$^2$), demonstrating a pronounced nonlinear optical response. Furthermore, the optical response properties are compared among various stable and metastable crystalline phases of TiO$_2$-rutile, anatase, brookite, TiO$_2$-II, and TiO$_2$-B-as well as an amorphous supercell model. These results provide microscopic insight into intensity-dependent optical degradation in TiO$_2$-based dielectric optical components exposed to intense femtosecond laser fields.
Comments25 pages, 7 figures
