In this article, we propose the design and analyze a plasmonic-organic-hybrid (POH) waveguide structure for efficient forward and backward second harmonic generation (SHG) to bridge the mid-infrared (IR) to near-IR. The required phase matching is satisfied by quasi-phase matching (QPM) technique through periodically altering the material of the metal-insulator-metal slot region between a nonlinear polymer (with second-order nonlinear coefficient of χ(2) ≠ 0) and Al2O3 (with χ(2) = 0) leading to modulation of χ(2) coefficient along the propagation direction. The strong field confinement offered by surface plasmon polaritons (SPPs) significantly enhances the normalized efficiency up to 1.75 × 106 W−1cm−2 in the case of backward SHG over a short device length of 17 μm with only 20 mW input power. Also, a slightly lower efficiency is achieved for forward configuration with broadband response, high fabrication tolerance, and small temperature-variation sensitivity. Furthermore, our proposed structure is based on standard nanofabrication technologies and can be used for all-optical signal processing, low-noise detection of a mid-IR signal in the near-IR windows, and (mirrorless) optical parametric oscillator.

中文翻译：

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等离子-有机混合结构中准相位匹配的二次谐波产生

在本文中，我们提出设计并分析等离子体-有机-混合 (POH) 波导结构，以实现有效的前向和后向二次谐波生成 (SHG)，以桥接中红外 (IR) 到近红外。所需的相位匹配通过准相位匹配 (QPM) 技术通过周期性改变非线性聚合物（二阶非线性系数为 χ(2) ≠ 0）和 Al2O3 之间的金属-绝缘体-金属槽区域的材料来满足（χ(2) = 0）导致 χ(2) 系数沿传播方向调制。表面等离子体激元 (SPP) 提供的强场限制在反向 SHG 的情况下，在仅 20 mW 输入功率的 17 μm 短器件长度上显着提高了归一化效率，最高可达 1.75 × 106 W−1cm−2。还，对于具有宽带响应、高制造公差和小温度变化敏感性的前向配置，实现了略低的效率。此外，我们提出的结构基于标准纳米制造技术，可用于全光信号处理、近红外窗口中中红外信号的低噪声检测和（无镜）光学参量振荡器。