High-Order Harmonic Generations in Epsilon-Near-Zero Aluminum-Doped Zinc Oxide Nanopyramid Array

We numerically demonstrate the high harmonic generations (HHGs) up to the seventh order in epsilon-near-zero (ENZ) aluminum-doped zinc oxide (AZO) nanopyramid array. Pumped by a 1-kHz repetition rate 50-mW 100-fs laser source at the telecommunication wavelength of 1550 nm, the conversion efficiencies of 1.41×10
^-5
, 3.64×10
^-6
, and 2.09×10
^-7
are achieved for third-, fifth-, and seventh-harmonic generations, respectively, which are comparable with the experimental results of indium tin oxide and indium-doped cadmium oxide. The electric field distributions, localized resonances, and emission patterns at HHG wavelengths are also discussed. The results of this work can be potentially useful in designing novel multiwavelength light sources for optical communication and on-chip light circuits.