With the help of a theoretical model and finite-difference time-domain (FDTD) simulations based on the hydrodynamic–Maxwell model, we examine the effect of difference-frequency generation (DFG) in an array of L-shaped metal nanoparticles (MNPs) characterized by intrinsic plasmonic nonlinearity. The outcomes of the calculations reveal the spectral interplay between gain and loss in the vicinity of the fundamental frequency of the localized surface plasmon resonances. Subsequently, we identify different array thicknesses and pumping regimes facilitating parametric amplification and spontaneous parametric downconversion. Our results suggest that the parametric amplification regime becomes feasible on a scale of hundreds of nanometers and spontaneous parametric downconversion on the scale of tens of nanometers, opening up new exciting opportunities for developing building blocks of photonic metasurfaces.

中文翻译：

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非线性等离子体纳米粒子阵列中增益和损耗之间的相互作用：走向参数下变频和放大

借助基于流体动力学-麦克斯韦模型的理论模型和时域有限差分 (FDTD) 模拟，我们研究了 L 形金属纳米颗粒 (MNP) 阵列中差频生成 (DFG) 的效果其特征在于固有的等离子体非线性。计算结果揭示了局域表面等离子体共振基频附近增益和损耗之间的光谱相互作用。随后，我们确定了不同的阵列厚度和泵浦方式，有利于参数放大和自发参数下变频。我们的结果表明，参数放大机制在数百纳米尺度上变得可行，并且自发参数下转换在数十纳米尺度上变得可行，为开发光子超表面构建块开辟了新的令人兴奋的机会。