The moiré effect is a universal phenomenon originating from the interference of waves, and it is widely applied in metrology as well as superconductor phenomena in graphene. The present study demonstrates a nonlinear moiré effect originating from the moiré superlattices of two nonlinear photonic crystals (NPCs). It is experimentally shown that these nonlinear moiré superlattices facilitate the nondestructive detection of nonlinear photonic crystals. Two identical periodically poled lithium niobates (PPLNs) are used to observe the nonlinear moiré effect originating from the nonlinear moiré superlattices. This is followed by a demonstration of the detection capability of the nonlinear optical method for dissimilar PPLNs and calculation of the period detection range. The theoretically and experimentally obtained periods of the target PPLN are consistent, and the resolution of the nonlinear moiré effect surpasses to that of presently used optical systems. Furthermore, the detection range of the nonlinear moiré effect enables the sub-micrometer- and nanometer-scale detection of the nonlinear photonic crystal structure using only an optical microscope. The present study conceptually extends the conventional moiré lattice to nonlinear optics, and it can also be extended to other fields where nonlinear effects cannot be avoided, such as polaritons and Bose–Einstein condensates.

中文翻译：

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用于非线性光子晶体超分辨率无损检测的非线性莫尔超晶格

莫尔效应是源于波的干涉的普遍现象，它广泛应用于计量以及石墨烯中的超导体现象。本研究证明了源自两个非线性光子晶体 (NPC) 的莫尔超晶格的非线性莫尔效应。实验表明，这些非线性莫尔超晶格有助于非线性光子晶体的无损检测。两个相同的周期性极化铌酸锂 (PPLN) 用于观察源自非线性莫尔超晶格的非线性莫尔效应。随后演示了非线性光学方法对不同PPLNs的检测能力和周期检测范围的计算。目标PPLN的理论和实验获得的周期是一致的，非线性莫尔效应的分辨率超过了目前使用的光学系统的分辨率。此外，非线性莫尔效应的检测范围使得仅使用光学显微镜即可对非线性光子晶体结构进行亚微米和纳米级检测。本研究在概念上将传统的莫尔晶格扩展到非线性光学，也可以扩展到其他非线性效应不可避免的领域，例如极化子和玻色-爱因斯坦凝聚。非线性莫尔效应的检测范围使得仅使用光学显微镜即可对非线性光子晶体结构进行亚微米和纳米级检测。本研究在概念上将传统的莫尔晶格扩展到非线性光学，也可以扩展到其他非线性效应不可避免的领域，例如极化子和玻色-爱因斯坦凝聚。非线性莫尔效应的检测范围使得仅使用光学显微镜即可对非线性光子晶体结构进行亚微米和纳米级检测。本研究在概念上将传统的莫尔晶格扩展到非线性光学，也可以扩展到其他非线性效应不可避免的领域，例如极化子和玻色-爱因斯坦凝聚。