Fig. 4: Field strength dependence of the four-wave mixing (FWM) in the low THz band for the parallel orientation of the TELBE and photoconductive antenna (PCA) fields.
From: Highly efficient broadband THz mixing and upconversion with Dirac materials
a Time-domain dynamics of the upconverted signal for different TELBE field strengths. The maximum field strength is \({E}_{{{{\rm{T}}}}}^{\max }\approx 86\,{{{\rm{kV}}}}\,{{{{\rm{cm}}}}}^{-1}\). Curves of different colors correspond to different peak field strengths. b Time-domain dynamics of the upconverted signal in the low THz band for different voltages VPCA applied to the PCA. The maximum field strength is \({E}_{{{{\rm{a}}}}}^{\max }\approx 6\,{{{\rm{kV}}}}\,{{{{\rm{cm}}}}}^{-1}\) for VPCA = 5 V. Curves of different colors correspond to different VPCA. c The FWM field \({E}_{{{{\rm{low}}}}}/{E}_{{{{\rm{low}}}}}^{\max }\) as a function of the normalized TELBE field strength for \({E}_{{{{\rm{a}}}}}={E}_{{{{\rm{a}}}}}^{\max }\). The red dashed line is a fit to \(\propto {({E}_{{{{\rm{T}}}}}/{E}_{{{{\rm{T}}}}}^{\max })}^{\beta }\) of the five experimental points with lower ET, yielding β = 1.6 ± 0.1. d The FWM field \({E}_{{{{\rm{low}}}}}/{E}_{{{{\rm{low}}}}}^{\max }\) as a function of the normalized PCA field strength for \({E}_{{{{\rm{T}}}}}={E}_{{{{\rm{T}}}}}^{\max }\). The red dashed line is a fit to \(\propto {({E}_{{{{\rm{a}}}}}/{E}_{{{{\rm{a}}}}}^{\max })}^{\beta }\) with β = 1.05 ± 0.05. Inset shows the upconversion efficiency for different time delays between the TELBE and PCA pulses. The uncertainty of \({E}_{{{{\rm{low}}}}}/{E}_{{{{\rm{low}}}}}^{\max }\) was obtained by estimating the error of Elow from the noise floor and propagating it to the ratio using standard Gaussian error propagation. For some points error bars are smaller than the symbol size and thus not visible.
