Giant second-harmonic generation in ferroelectric NbOI2
Giant second-harmonic generation in ferroelectric NbOI2
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DOI：
10.1038/s41566-022-01021-y
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发表时间：
2022-06-30
期刊：
影响因子：
35
通讯作者：
Loh, Kian Ping
中科院分区：
文献类型：
--
作者：
Abdelwahab, Ibrahim;Tilmann, Benjamin;Loh, Kian Ping
在纳米尺度的光子器件中实现非线性光学元件面临着需要数百个波长量级的厚度的相位匹配条件的挑战，并且受到纳米材料的光学相互作用深度短和弱光子-光子相互作用的不利影响。在这里，我们报道了铁电NbOI2纳米片显示出巨大的二次谐波产生，其转换效率比通常报道的非线性晶体高出一个数量级。在平均泵浦强度为8kW cm~(-2)时，获得了约0.2%的绝对倍频转换效率和约10(-9)mV~(-1)量级的有效非线性极化率。由于NbO_2中各向异性极化和激子共振的相互作用，极化倍频响应的空间分布可以通过激发波长来调节。我们的结果为超薄、高效的非线性光学元件提供了一种新的范例。
Implementing nonlinear optical components in nanoscale photonic devices is challenged by phase-matching conditions requiring thicknesses in the order of hundreds of wavelengths, and is disadvantaged by the short optical interaction depth of nanometre-scale materials and weak photon-photon interactions. Here we report that ferroelectric NbOI2 nanosheets exhibit giant second-harmonic generation with conversion efficiencies that are orders of magnitude higher than commonly reported nonlinear crystals. The nonlinear response scales with layer thickness and is strain- and electrical-tunable; a record >0.2% absolute SHG conversion efficiency and an effective nonlinear susceptibility chi((2))(eff) in the order of 10(-9) m V-1 are demonstrated at an average pump intensity of 8 kW cm(-2). Due to the interplay between anisotropic polarization and excitonic resonance in NbOI2, the spatial profile of the polarized SHG response can be tuned by the excitation wavelength. Our results represent a new paradigm for ultrathin, efficient nonlinear optical components.