High-harmonic generation (HHG) from solids in non-perturbative regime has recently attracted great interest due to the high efficiency compared with atomic gaseous media, compact experimental configurations, and promising applications for spectroscopy and coherent extreme ultraviolet sources. However, it needs still high pump intensity in the order of several hundreds GW/cm². In this work, we present comprehensive results of efficient HHG with low pump threshold by employing high field enhancements in dielectric metasurfaces and hybrid metasurfaces comprising plasmonic nanoantennae. The numerical results show that ZnO nanodisk arrays supported by gold substrate enable us to generate high-order harmonics with efficiency in the order of 10⁻⁵–10⁻⁶% in plateau region and cut-off order of up to 21 by pumping at 1550 nm with a peak intensity below 70 GW/cm². When using metasurfaces of plasmonic nanoantennae containing ZnO nanoparticles in their gaps and supported by dielectric substrate, HHG can be realized by using pump with much lower peak intensity and the spatial inhomogeneity of plasmon-induced local field plays an important role, leading to the appearance of even order harmonics. For peak pump intensity of about 0.4 GW/cm², the resultant HHG efficiency in plateau region is in the orders of 10⁻⁸% for odd order harmonics and 10⁻⁹% for even order ones. In particular, when the plasmonic metasurfaces are supported by dielectric-coated metallic substrate, the local field in the gap region is further enhanced, resulting in HHG efficiency 1–2 orders-of-magnitude higher than the case of using dielectric substrate.

由于与原子气态介质相比效率高，紧凑的实验配置以及在光谱学和相干极紫外光源方面的应用前景广阔，因此在非扰动状态下由固体产生高谐波（HHG）引起了人们的极大兴趣。但是，仍然需要几百GW / cm ²量级的高泵浦强度。在这项工作中，我们通过在包含等离子体等离子体纳米天线的介电超颖表面和混合超颖表面中采用高场增强，展示了具有低泵浦阈值的高效HHG的综合结果。数值结果表明，金基底支撑的ZnO纳米磁盘阵列使我们能够以10 ^-5 –10 ^-6的效率产生高次谐波。通过在1550 nm处泵浦，峰值强度低于70 GW / cm ^2，在高原区域中的浓度百分比最高，截止值最高可达21 。当使用在间隙中包含ZnO纳米粒子并由电介质基底支撑的等离激元纳米天线的超表面时，可以通过使用具有低得多的峰值强度的泵来实现HHG，并且等离激元诱导的局部场的空间不均匀性起着重要作用，从而导致出现偶次谐波。对于约0.4 GW / cm ^2的峰值泵浦强度，高原区域的合成HHG效率对于奇次谐波和10 ^-9约为10 ^-8％。％代表偶数。特别是，当等离子超表面由介电涂层的金属基板支撑时，间隙区域中的局部电场会进一步增强，导致HHG效率比使用介电基板的情况高1-2个数量级。