Fig. 4: Pockels coefficients of LN and BTO.

a, Pockels coefficient measurements for LN, with r₃₃ in dark blue, r₄₂ in light blue and linear fits to the data in solid lines. The fitted values are r₃₃ = 26.9 pm V^–1 and 1/2(r₁₃ + 2r₄₂) = 15.0 pm V^–1. b, Pockels coefficient measurements for BTO, with r₃₃ in dark green, r₄₂ in light green and model fits to the data in solid lines. The r₄₂ data are fit to a Debye model with γ₀ = 565 MHz, σ = 0.06, S_R = 75 pm V^–1 and r_∞ = 60 pm V^–1. The 1/2(r₁₃ + 2r₄₂) value is fit using equation (5), where ε is calculated from the Debye model of equation (2) using the same coefficients as the measured permittivity (Table 1). The data points are the result of fitting the measured r_eff data from n = 15–20 devices to equation (4), as described in Supplementary Information. The error bars represent two standard errors of the fit. Note that typically 2r₄₂ ≫ r₁₃ so that r₁₃ + 2r₄₂ ≈ 2r₄₂. We, therefore, plot this parameter as 1/2(r₁₃ + 2r₄₂) ≈ r₄₂.