Nonlinear photonic crystals are microstructures with quadratic nonlinearity (${\chi ^{(2)}}$) that have been extensively used for the generation and control of coherent light at new frequencies. Thanks to the recent invention of 3D ${\chi ^{(2)}}$-nonlinearity engineering techniques using femtosecond laser pulses, studies of intense light interaction with 3D nonlinear photonic crystals are now experimentally feasible. Here we review the latest research advances in nonlinear photonic crystals, focusing especially on the fabrication, characterization, and application of 3D structures. We also discuss the future development of 3D nonlinear photonic crystals with properties and functionalities that are either difficult or virtually impossible to achieve with lower dimensional structures.

中文翻译：

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非线性光子晶体：从2D到3D

非线性光子晶体是具有二次非线性（$ {\ chi ^ {（2）}} $）的微结构，已被广泛用于在新频率下产生和控制相干光。由于使用飞秒激光脉冲的3D $ {\ chi ^ {（2）}} $-非线性工程技术的最新发明，研究与3D非线性光子晶体的强光相互作用现在在实验上是可行的。在这里，我们将回顾非线性光子晶体的最新研究进展，重点关注3D结构的制造，表征和应用。我们还将讨论具有3D非线性光子晶体的未来发展，这些晶体的特性和功能在低维结构中很难或几乎不可能实现。