Fig. 4: Impact of the nanoantenna geometry on the wavelength conversion efficiency.
From: Wavelength conversion through plasmon-coupled surface states
a–f Top: The induced current on the nanoantennas as a function of frequency when the nanoantenna length (La) is varied from 1 to 9 μm. The ground line width (Lb) and the gap between the nanoantenna array rows (Lg) are chosen as 2 and 0.5 μm. The ground line is located between −2 μm and 0 positions and the nanoantenna is located between 0 and 1–9 μm positions along the z-axis. a–f Bottom: Decomposition of the total induced current on the nanoantennas (teal lines) to the individual contributions of the injected currents from different positions of the nanoantennas (white lines) at 0.2 THz. The background color maps show the electron generation profiles averaged over the nanoantenna width. Predicted and measured terahertz radiation power from fabricated nanoantenna arrays with different nanoantenna lengths, ground line widths, and gap sizes between the nanoantenna rows are shown in h, i, and j respectively. All the fabricated nanoantenna arrays have a 1 × 1 mm2 area and are characterized using the same optical pulses with 120 fs pulse width, 2.63 nJ pulse energy, and 76 MHz repetition rate.
