This research examines the thermally-induced nonlinear optical properties of Ti-Al-oxide nano-films. The Ti-Al nano-layer system was sequentially evaporated on glass and c-Si(100) substrates at room temperature. The Ti layers were spontaneously oxidized by the residual oxygen of the background vacuum in the deposition chamber. The Al layer, on the other hand, was partially oxidized and contained metallic inclusions. However, when oxygen was deliberately introduced into the chamber, the Al layer was oxidized with smaller inclusions. We experimentally demonstrate the existence of double epsilon-near-zero (2ENZ) behavior in the oxidized Al films by directly measuring the dielectric permittivity through ellipsometric analysis. The Maxwell-Garnett theory for a composite film formed by a mixture of Al and TiO₂ inclusions in Ti-Al-oxide matrix was used to predict the two cross-over points of the ENZ behavior. Enhancement in the nonlinear optical response near the ENZ points was obtained.

中文翻译：

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双ε-近零行为的Ti-Al氧化物纳米薄膜的热诱导非线性光学性质

这项研究检查了热诱导的钛铝氧化物纳米薄膜的非线性光学性质。Ti-Al纳米层系统在室温下依次在玻璃和c-Si（100）基板上蒸发。Ti层在沉积室中被背景真空中的残留氧气自发氧化。另一方面，Al层被部分氧化并且包含金属夹杂物。然而，当有意将氧气引入腔室时，Al层被较小的夹杂物氧化。我们通过椭偏分析直接测量介电常数，通过实验证明了在氧化的Al膜中存在双ε-接近零（2ENZ）行为。麦克斯韦-加纳特理论关于由Al和TiO ₂的混合物形成的复合膜Ti-Al-氧化物基质中的夹杂物用于预测ENZ行为的两个交叉点。在ENZ点附近获得了非线性光学响应的​​增强。