We report a large third-order nonlinear-optical response of palladium diselenide (PdSe₂) films, a two-dimensional (2D) noble-metal dichalcogenide material. Both open-aperture (OA) and closed-aperture (CA) Z-scan measurements are performed with a femtosecond pulsed laser at 800 nm to investigate the nonlinear absorption and nonlinear refraction, respectively. In the OA experiment, we observe optical limiting behavior originating from large two-photon absorption (TPA) in the PdSe₂ film of β = 3.26 × 10^–8 m/W. In the CA experiment, we measure a peak–valley response corresponding to a large and negative Kerr nonlinearity of n₂ = −1.33 × 10^–15 m²/W, 2 orders of magnitude larger than that of bulk Si. We also characterize the variation of n₂ as a function of the laser intensity, observing that n₂ decreases in magnitude with incident laser intensity, becoming saturated at n₂ = −9.96 × 10^–16 m²/W at high intensities. These results verify the large third-order nonlinear-optical response of 2D PdSe₂ as well as its strong potential for high-performance nonlinear photonic devices.

中文翻译：

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纳米厚的PdSe ₂ 2D二硫属化物膜中的大三阶光学Kerr非线性：对非线性光子器件的影响

我们报告了二维（2D）贵金属二卤化镓材料二硒化钯（PdSe ₂）薄膜的大三阶非线性光学响应。用孔径为800 nm的飞秒脉冲激光进行开孔（OA）和闭孔（CA）Z扫描测量，分别研究非线性吸收和非线性折射。在OA实验中，我们观察到源自PdSe ₂膜中的大双光子吸收（TPA）的光学限制行为，β= 3.26×10 ^–8 m / W。在CA实验中，我们测量了峰谷响应，其对应于n ₂ = −1.33×10 ^–15 m ²的较大的负克尔非线性/ W，比块状Si大2个数量级。我们还将n ₂的变化表征为激光强度的函数，观察到n ₂随入射激光强度的变化而减小，在高强度下n ₂ = -9.96×10 ^–16 m ² / W时达到饱和。这些结果证明了2D PdSe ₂的大三阶非线性光学响应以及其对于高性能非线性光子器件的强大潜力。