Figure 1.

Metamaterial for artificial high harmonic generation. (a) Schematic of metamaterial with the polarization state of harmonics indicated. (b) Unit cell of metamaterial. In terahertz regime, the geometric constants are as follows: P=30 μm, l₁=15.6 μm, w₁=2.5 μm, w₂=3 μm, l₂=8.6 μm, g=2 μm, and d=1 μm. The relations of the localized magnetic field B(ω), the drift velocity of the free electrons v(ω), and the magnetic force F_B(ω) for 2^nd (c), 3^rd (d), and 4^th (e) harmonics with the corresponding orientations of the polarizations marked.