Fig. 4
Near-IR laser intensity and gate voltage-dependence of d11-SHG. a Voltage-controlled normalized conversion efficiency (\(\eta _\omega = P_\omega /P_\omega ^2\)) of d11-SHG under different excitation intensity of the fundamental wave. b I–V curve under different laser excitation intensity. c Near-IR intensity dependence of η2ω at −70 V bias, which is within the saturation region or at which the high-field domain overlaps with the IR excitation region completely (supplementary Fig. 4c). d IR intensity dependence of η2ω at −30 V bias at which only the domain boundary reaches the near-IR excitation region (Supplementary Fig. 4c). The SHG at -30V was also calculated from the field strength of the high-field domain with the experimental excitation intensity and SHG conversion efficiency. More details can be found in Supplementary Note 5. e, Gate-controlled SHG (black curve) and current (red curve). The high-field domain is formed over the near-IR excitation when VDS = 80 V (Supplementary Fig. 5b)
