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Doubly-Resonant Enhancement of Second Harmonic Generation from a WS2 Nanomesh Polymorph with a Modified Energy Landscape
Laser & Photonics Reviews ( IF 11.0 ) Pub Date : 2021-05-10 , DOI: 10.1002/lpor.202100117
Alexander W. A. Murphy 1, 2, 3 , Zichen Liu 2, 3, 4 , Andrey V. Gorbach 1, 3 , Adelina Ilie 2, 3, 4 , Ventsislav K. Valev 1, 2, 3
Affiliation  

Although transition metal dichalcogenides (TMDs, e.g., WS2, WSe2, MoS2, MoSe2) have emerged as highly promising 2D materials for nonlinear optics, they are limited by intrinsically small light-matter interaction length and (typically) flat-lying geometries. The first hyperspectral multiphoton analysis of a tridimensional webbed network of densely-packed stacks (of 1–5 layers) of twisted and/or fused 2D nanosheets of WS2, referred to as “nanomesh”, is presented here. The optical second harmonic generation (SHG) is mapped across the three characteristic spectral features (A, B, and C) and two-photon luminescence and third harmonic generation signatures are established. Compared to flat-lying WS2 layers, the nanomesh is highly efficient, broadband, and robust against degradation (with main enhancement originating from the C feature, spreading from 850 to 1100 nm), and scalable in terms of growth. The origin of these spectral differences is assigned to hotspots, whose location changes depending on the wavelength of illumination. The main SHG enhancements result from double resonances in an energy landscape modified by in-built defects (e.g., vacancies and their passivated variants, or grain boundaries) that induce intra-bandgap energy levels. These characteristics establish the nanomesh as a prime candidate for integration into quantum optical technologies, such as miniaturized devices on chip.

中文翻译:

具有修正能量景观的 WS2 纳米网格多晶型二次谐波产生的双共振增强

尽管过渡金属二硫属化物(TMD,例如 WS 2、WSe 2、MoS 2、MoSe 2)已成为非常有前途的非线性光学二维材料,但它们受到本质上很小的光-物质相互作用长度和(通常)平坦的限制几何形状。此处介绍了对 WS 2扭曲和/或融合二维纳米片(称为“纳米网” )的密集堆叠(1-5 层)三维网状网络的第一次高光谱多光子分析。光学二次谐波生成 (SHG) 映射到三个特征光谱特征(A、B 和 C),并建立双光子发光和三次谐波生成特征。与平躺 WS 2相比层,纳米网格是高效的、宽带的、抗退化的(主要增强来自 C 特征,从 850 到 1100 nm),并且在增长方面可扩展。这些光谱差异的起源被指定为热点,其位置根据照明波长而变化。主要的 SHG 增强是由内在缺陷(例如,空位及其钝化变体或晶界)修改的能量景观中的双共振引起的,这些缺陷引起带隙内能级。这些特性使纳米网格成为集成到量子光学技术(例如芯片上的小型化设备)中的主要候选者。
更新日期:2021-06-10
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