非线性超构表面:谐波产生与超快调控

超构表面是指由亚波长结构构成的纳米光学天线阵列。在合适的激发条件下，纳米天线可以产生共振，实现近场增强，进而增强非线性光学效应。相较于传统非线性光学晶体，超构表面集成度较高，有利于实现小型化的高效非线性光源。由于光只传播亚波长的距离，针对非线性谐波产生等应用，超构表面具有无需考虑相位匹配的优势。此外，超构表面具有亚波长的空间分辨率，通过对结构单元的设计和排列，可以实现对非线性谐波的相位、偏振和振幅的灵活调控。该综述针对超构表面在光学频率转换、非线性波前调控以及超快全光调控等领域的国内外近期工作进行了总结，并对非线性超构表面在走向实际应用中面临的挑战和进一步的发展方向进行了展望。

Nonlinear metasurfaces: harmonic generation and ultrafast control

Metasurfaces refer to the optical nanoantenna arrays composed of subwavelength structures. Nanoantennas can have resonances under appropriate excitation conditions, to achieve near-field enhancement, and thus enhancing nonlinear optical effects. Compared with conventional nonlinear optical crystals, metasurfaces are more compact, with the possibility for on-chip integration. Due to the subwavelength light-matter interaction length, for applications such as nonlinear harmonic generation, metasurfaces does not suffer from the limitation of phase-matching. In addition, metasurfaces own the subwavelength spatial resolution. By designing and arranging the meta-atoms, metasurfaces can realize flexible control of the phase, polarization, and amplitude of the harmonic wave. Recent works on nonlinear metasurfaces for applications in optical frequency conversion, nonlinear wavefront control and ultrafast all-optical modulation were reviewed, the challenges and perspectives for the practical application of metasurfaces were presented.