Gap-Plasmon-Enhanced Second-Harmonic Generation in Epsilon-Near-Zero Nanolayers,ACS Photonics

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Gap-Plasmon-Enhanced Second-Harmonic Generation in Epsilon-Near-Zero Nanolayers
ACS Photonics ( IF 6.5 ) Pub Date : 2019-12-23 , DOI: 10.1021/acsphotonics.9b01350
Chandriker Kavir Dass _{1,

2} , Hoyeong Kwon ₃ , Shivashankar Vangala ₁ , Evan M. Smith _{1,

2} , Justin W. Cleary ₁ , Junpeng Guo ₄ , Andrea Alù _{3,

5,

6,

7} , Joshua R. Hendrickson ₁

Affiliation

With the ability to confine light to subwavelength volumes, plasmonic nanostructures and metamaterials have proven to be powerful tools for nanophotonic applications. For nonlinear processes, however, the small dimensions of nanophotonic devices can become problematic, as phase-matching techniques—designed to increase interaction lengths—are no longer applicable. In this work, we utilize the field confining properties of plasmonic nanoparticles in a modified metal–insulator–metal (MIM) patch nanoantenna to efficiently couple to an epsilon-near-zero (ENZ) mode in a nanolayer film of indium tin oxide (ITO). The modified MIM device differs from traditional MIM structures in that the insulator spacing layer makes use of a low-index, 12 nm nanolayer ITO film on top of a higher index SiO₂ layer, allowing for highly confined electric fields. Combined with the enhanced nonlinear response at the ENZ point of the ITO film, we are able to achieve second-harmonic generation (SHG) enhancements of up to 50 000 relative to off-device performance with no patch antenna present. In addition, simulations and reflectivity measurements show near perfect absorption (>98%) over a range of 245 nm centered around 1550 nm, enabling tunable SHG generation—with enhancement factors over 10⁴—that is experimentally demonstrated over a spectral range of 125 nm. Although this work is done in the telecom regime, the modified MIM structure can be applied to a wide variety of wavelengths, limited only by device scaling and suitable stackings of low- and high-index insulator materials within the spacer layer.

中文翻译：

Epsilon-Near-Zero纳米层中间隙等离子增强的二次谐波产生。

具有将光限制在亚波长范围内的能力，等离子体纳米结构和超材料已被证明是用于纳米光子应用的强大工具。但是，对于非线性过程，纳米光子器件的小尺寸可能会成为问题，因为旨在增加相互作用长度的相位匹配技术已不再适用。在这项工作中，我们利用修饰的金属-绝缘体-金属（MIM）贴片纳米天线中的等离激元纳米粒子的场约束特性，以有效地耦合到铟锡氧化物（ITO）纳米膜中的ε近零（ENZ）模式。）。改进的MIM器件与传统MIM结构的不同之处在于，绝缘体间隔层在高折射率SiO _2的顶部使用了低折射率的12 nm纳米层ITO膜层，允许高度受限的电场。结合ITO膜ENZ点处增强的非线性响应，我们可以在不存在贴片天线的情况下实现相对于器件外性能高达5万次的二次谐波生成（SHG）增强。此外，仿真和反射率测量结果表明，在以1550 nm为中心的245 nm范围内，吸收率接近完美（> 98％），可生成可调的SHG（增强系数超过10 ^4），这在125 nm的光谱范围内得到了实验证明。尽管这项工作是在电信领域完成的，但修改后的MIM结构可以应用于各种波长，仅受器件缩放以及隔离层内低折射率和高折射率绝缘体材料适当堆叠的限制。

更新日期：2019-12-25

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