Comparative Study of Second-Harmonic Generation from Epsilon-Near-Zero Indium Tin Oxide and Titanium Nitride Nanolayers Excited in the Near-Infrared Spectral Range
Comparative Study of Second-Harmonic Generation from Epsilon-Near-Zero Indium Tin Oxide and Titanium Nitride Nanolayers Excited in the Near-Infrared Spectral Range
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DOI：
10.1021/acsphotonics.5b00355
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发表时间：
2015-11-01
期刊：
影响因子：
7
通讯作者：
Dal Negro, Luca
中科院分区：
文献类型：
--
作者：
Capretti, Antonio;Wang, Yu;Dal Negro, Luca
我们进行了二次谐波产生（SHG）从铟锡氧化物（ITO）和从氮化钛（TiN）纳米层在近红外光谱激发的比较研究。这两种材料都与Si技术兼容，是集成非线性光学的候选平台。在这项工作中，我们制造的ITO样品的电子接近零（ENZ）的条件，它可以在1150-1670 nm的光谱范围内连续定制，和TiN样品在相同的光谱范围内的金属行为。对于ITO纳米层，我们观察到的可调谐性和增强的SHG强度时，样品被激发在各自的ENZ条件，在协议的电磁建模和类似的三次谐波产生之前研究。另一方面，我们表明TiN纳米层的SHG效率降低了50倍。我们通过实验确定了我们最好的ITO纳米层的二阶极化率的主要分量是chi（（2 Ω））（zzz））= 0.18 pm V-1，并且我们理论上预测，当相对于2000 nm的波长在ENZ波长下共振泵浦纳米层时，SHG过程增强高达4个数量级。值得注意的是，所得的SHG效率与在我们的反射配置实验中用作参考的厚度为0.5 mm的晶体石英板相当。我们的研究清楚地表明，具有工程ENZ条件的ITO纳米层是表面非线性的一个有前途的材料平台，可能应用于非线性超颖表面，Si基平面光学和传感。
We perform a comparative study of second-harmonic generation (SHG) from indium tin oxide (ITO) and from titanium nitride (TiN) nanolayers excited in the near-infrared spectrum. Both materials are compatible with Si technology and are candidate platforms for integrated nonlinear optics. In this work, we fabricate ITO samples with an e-near-zero (ENZ) condition, which can be continuously tailored in the 1150-1670 nm spectral range, and TiN samples with a metallic behavior in the same spectral range. For the ITO nanolayers, we observe tunability and enhancement of the SHG intensity when the samples are excited at their respective ENZ condition, in agreement with the electromagnetic modeling and analogous to its third-harmonic generation studied earlier. On the other hand, we show that the SHG efficiency of TiN nanolayers is lower by a factor of 50. We determine experimentally that the dominant component of the second-order susceptibility for our best ITO nanolayer is chi((2 omega))(zzz)) = 0.18 pm V-1, and we theoretically predict that the SHG process is enhanced up to 4 orders of magnitude when resonantly pumping the nanolayer at the ENZ wavelength with respect to a wavelength at 2000 nm. Remarkably, the resulting SHG efficiency is comparable with a crystalline quartz plate with thickness 0.5 mm used as a reference in our experiments in reflection configuration. Our study clearly indicates that ITO nanolayers with engineered ENZ conditions are a promising material platform for surface nonlinearities, with possible applications to nonlinear metasurfaces, Si-based flat optics, and sensing.