Although periodic photonic structures, especially associated with nonlinearity, play a prominent role in optics nowadays, effective detection of their nonlinearity still remains a critical challenge. Here, an approach is proposed to detect the nonlinearity of photonic lattices in a direct way. By properly launching structured beams, namely Airy beams, into the lattices, the nonlinear response function of the discrete system can be directly obtained in the nonlinearly‐shaped beam profiles. To be specific, a single Airy beam is utilized to map self‐defocusing nonlinearity, while self‐focusing nonlinearity, which is hard to visualize in the bulk case, is readily discerned by employing double Airy beams in photonic structures. The proposed method is validated numerically and experimentally by detecting different types of nonlinearities of photonic lattices fabricated in a nonlinear crystal. These findings introduce a promising route for characterizing the nonlinear response of optical structures, thereby broadening the scope of nonlinear measurement and is expected to be extended into other periodic photonic structures.

中文翻译：

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光子晶格中的非线性检测


尽管周期性光子结构，尤其是与非线性相关的光子结构，在当今光学中发挥着重要作用，但有效检测其非线性仍然是一个关键挑战。在这里，提出了一种直接检测光子晶格非线性的方法。通过将结构光束（即 Airy 光束）正确发射到晶格中，可以直接在非线性形状的光束轮廓中获得离散系统的非线性响应函数。具体来说，单个艾里光束用于映射自离焦非线性，而自聚焦非线性在体件中难以可视化，而通过在光子结构中使用双艾里光束很容易识别。通过检测非线性晶体中制造的光子晶格的不同类型的非线性，对所提出的方法进行了数值和实验验证。这些发现为表征光学结构的非线性响应引入了一条有前途的路线，从而拓宽了非线性测量的范围，并有望扩展到其他周期性光子结构。