Figure 6

Calculated mid-IR-to-THz conversion efficiency for the tested devices as a function of mid-IR pump frequencies ω₁ and ω₂ assuming Γ₂₃ = 4 meV near threshold (a), in the middle of dynamic range (b) and near the rollover point (c–e) Calculated mid-IR-to-THz conversion efficiency for tested devices as a function of mid-IR pump frequencies close to the rollover point and assuming Γ₂₃ = 2 meV (d) and Γ₂₃ = 8 meV (e,f) Cross section data comparison between theory and experiment. Black circles are experimental data taken along white dashed line in Fig. 4(f); red, blue and green lines are the theoretical values taken along white dashed line in panels (d,c,e). Theoretical data with the linewidth factor Γ₂₃ = 4 meV provides the best match to the experimental data.