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arXiv 2301.08089physics.optics
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纳米层压结构中增强的表面二次谐波产生

Enhanced Surface Second Harmonic Generation in Nanolaminates

Fatemeh Abtahi, Pallabi Paul, Sebastian Beer, Athira Kuppadakkath, Anton Pakhomov, Adriana Szeghalmi, Stefan Nolte, Frank Setzpfandt, Falk Eilenberger

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AI总结：

本文通过PEALD制备SiO2/TiO2亚波长纳米层压结构，利用大量界面增强表面二次谐波产生，实验证实大入射角下SHG显著增强且与理论计算吻合。

摘要：

二次谐波产生（SHG）是一种二阶非线性光学过程，在具有反演对称性的介质中是不允许发生的。然而，由于表面处对称性的破缺，表面SHG仍然会发生，但通常强度较小。我们实验研究了由交替的亚波长介电层组成的周期性堆叠结构中的表面SHG，这种结构具有大量的表面，从而显著增强了表面SHG。为此，我们采用等离子体增强原子层沉积（PEALD）技术在熔融石英衬底上生长了SiO2/TiO2多层堆叠结构。利用该技术可以制备单层厚度小于2 nm的薄膜。我们实验证明，在大入射角（>20度）条件下，存在显著的SHG，其强度远超简单界面所能观测到的水平。我们针对具有不同周期和SiO2/TiO2厚度的样品开展了该实验，实验结果与理论计算一致。

英文摘要：

Second-harmonic generation (SHG) is a second-order nonlinear optical process that is not allowed in media with inversion sym-metry. However, due to the broken symmetry at the surface, surface SHG still occurs, but is generally small. We experimentally investi-gate the surface SHG in periodic stacks of alternating, subwave-length dielectric layers, which have a large number of surfaces, thus enhancing surface SHG considerably. To this end, multilayer stacks of SiO2/TiO2 were grown by Plasma Enhanced Atomic Layer Deposition (PEALD) on fused silica substrates. With this technique individual layers of a thickness of less than 2 nm can be fabricated. We experimentally show that under large angles of incidence (> 20 degrees) there is substantial SHG, well beyond the level, which can be observed from simple interfaces. We perform this experiment for samples with different periods and thickness of SiO2/TiO2 and our results are in agreement with theoretical calculations.

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