Platinum diselenide (PtSe2), classified as a noble metal dichalcogenide, has garnered substantial interest owing to its layer-dependent band structure, remarkable air-stability, and high charge-carrier mobilities. These properties make it highly promising for a wide array of applications in next-generation electronic and optoelectronic devices, as well as sensors. Additionally, two-dimensional (2D) PtSe2 demonstrates significant potential as a saturable absorber due to its exceptional nonlinear optical response across an ultrabroad spectra range, presenting exciting opportunities in ultrafast and nonlinear photonics. In this work, we explore the second-order nonlinear optical characteristics of 2D PtSe2 by analyzing its second-harmonic generation (SHG) excited by a pulsed laser at 1064 nm. Our investigation unveils a layer-dependent SHG response in PtSe2, with prominent SHG intensity observed in few-layer PtSe2. The distinct six-fold polarization dependence pattern observed in the SHG intensity reflects the inherent threefold rotational symmetry inherent to the PtSe2 crystal structure. Remarkably, the SHG intensity of 4-layer PtSe2 surpasses that of mechanically exfoliated monolayer molybdenum disulfide (MoS2) by approximately two orders of magnitude (60-fold), underscoring its exceptional second-order nonlinear optical response. Combined with its ultrahigh air-stability, these distinctive nonlinear optical characteristics position two-dimensional PtSe2 as a promising candidate for ultrathin nonlinear nanophotonic devices.

中文翻译：

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二维 PtSe2 中强烈的二次谐波产生

二硒化铂 (PtSe2），被归类为贵金属二硫属化物，由于其层依赖的能带结构、显着的空气稳定性和高载流子迁移率而引起了广泛的兴趣。这些特性使其在下一代电子和光电设备以及传感器的广泛应用中极具前景。此外，二维 (2D) PtSe2由于其在超宽光谱范围内出色的非线性光学响应，展现出作为可饱和吸收体的巨大潜力，为超快和非线性光子学带来了令人兴奋的机会。在这项工作中，我们探索了二维 PtSe 的二阶非线性光学特性2通过分析 1064 nm 脉冲激光激发的二次谐波 (SHG)。我们的研究揭示了 PtSe 中层依赖的 SHG 响应2，在少层 PtSe 中观察到显着的 SHG 强度2。在 SHG 强度中观察到的独特的六重偏振依赖性模式反映了 PtSe 固有的三重旋转对称性2晶体结构。值得注意的是，4 层 PtSe 的 SHG 强度2超过机械剥离单层二硫化钼（MoS2）大约提高了两个数量级（60 倍），凸显了其卓越的二阶非线性光学响应。结合其超高的空气稳定性，这些独特的非线性光学特性定位了二维 PtSe2作为超薄非线性纳米光子器件的有前途的候选者。