Halide perovskite nanocrystals are suitable materials for photonic devices because their highly efficient luminescence can be tuned over a wide wavelength range by changing the nanocrystal composition and size. Here, we report on the high-order harmonic generation in a solution-processed perovskite ${\mathrm{CsPbBr}}_3$ nanocrystal film that is excited by a strong midinfrared laser. We observe harmonics up to the 13th order, which is ultraviolet light well above the band-gap energy. By using elliptically polarized laser light, we analyze the influence of the sample structure on the intensity of the 5th harmonic. It is also found that the randomness in the orientation of the nanocrystals in the film induces a reduction in the harmonic intensities due to the interference among the harmonics emitted from nanocrystals with different phases. Our observation of high-order harmonics from nanocrystal films opens a way towards the development of an intensity modulator that can be tuned simply by changing the excitation ellipticity.

中文翻译：

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椭圆偏振激光激发胶态钙钛矿纳米晶体对高次谐波的干扰效应

钙钛矿卤化物纳米晶体是适合光子器件的材料，因为可以通过改变纳米晶体的组成和尺寸在很宽的波长范围内调节其高效发光。在这里，我们报告固溶钙钛矿中高次谐波的产生${\mathrm{溴化铯}}_3$被强中红外激光激发的纳米晶体薄膜。我们观察到高达13阶的谐波，这是远高于带隙能量的紫外线。通过使用椭圆偏振激光，我们分析了样品结构对五次谐波强度的影响。还发现，由于从具有不同相的纳米晶体发射的谐波之间的干扰，膜中纳米晶体的取向的随机性引起谐波强度的降低。我们对来自纳米晶体薄膜的高次谐波的观察为开发强度调制器开辟了道路，该强度调制器可以通过简单地改变激发椭圆率来进行调谐。