电子结构调控对MgO非线性光学性质的影响
Controlling the nonlinear optical properties of MgO by tailoring the electronic structure
摘要：
物质对高电场的非线性响应的研究最近已经包括在近红外（NIR）驱动波长下固体中的谐波产生。超快信号处理和固体中电子波函数的全光学映射的前景引起了人们的兴趣。工程固态能带结构来控制非线性过程已经在理论上得到重视。在这里，我们实验表明，第一次二次谐波产生（SHG）可以通过掺杂晶体的氧化镁（MgO）与铬（Cr）原子。我们发现，增强的程度依赖于非线性的掺杂剂浓度。当Cr掺杂剂引入纯MgO中时，SHG效率增加。Cr掺杂剂的效果的物理图片是由密度泛函理论（DFT）计算的纯和掺杂样品的电子结构的帮助。这项工作表明，通过修改电子结构的二次谐波效率的明确增强。所观察到的效果是一致的电子结构，有利于表面诱导的SHG，并表现出最小的角度依赖性。这项工作突出了操纵固体的电子结构来控制或测试其非线性光学响应理论的潜力。
英文摘要：
The study of the non-linear response of matter to high electric fields has recently encompassed harmonic generation in solids at near-infrared (NIR) driving wavelengths. Interest has been driven by the prospect of ultrafast signal processing and all-optical mapping of electron wave-functions in solids. Engineering solid-state band structures to control the non-linear process has already been highlighted theoretically. Here, we show experimentally for the first time that second harmonic generation (SHG) can be enhanced by doping crystals of magnesium oxide (MgO) with chromium (Cr) atoms. We show that the degree of enhancement depends non-linearly on dopant concentration. The SHG efficiency is shown to increase when Cr dopants are introduced into pure MgO. A physical picture of the effect of Cr dopants is aided by density functional theory (DFT) calculations of the electronic structure for pure and doped samples. This work shows an unambiguous enhancement of the SHG efficiency by modifying the electronic structure. The observed effects are consistent with an electronic structure that facilitates the surface induced SHG and demonstrates a minimal angular dependence. This work highlights the potential of manipulating the electronic structure of solids to control or test theories of their non-linear optical response.
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