Interferometric determination of the temperature dependence of the refractive index of relaxor PLZT ceramics under DC bias

Abstract

Changes in the refractive indices Δ n 1 and Δ n 3 of clamped transparent relaxor ferroelectric (9.5/65/35) and (9.0/65/35) PLZT ceramics were measured as a function of temperature ranging from −30 °C to 60 °C, and at various transversely applied DC electric fields E 3 DC . It was found that the refractive index of both PLZT compositions increased linearly with temperature under no DC bias, indicating a constant electronic polarizability of the samples in the tested temperature range. The rate of increase of Δ n 3 with temperature became higher for both compositions upon the application a DC bias field ( E 3 DC = 774 kV / m ) due to increased electronic polarizability of the samples, while the rate of increase of Δ n 1 with temperature remained unchanged and was independent of the DC field applied. The quadratic electro-optic coefficients of these two PLZT compositions were also obtained at 0, 20 and 40 °C, and a significant non-linearity was observed: an 85% decrease in the electro-optic coefficient of PLZT (9.5/65/35) was measured at 40 °C compared to 0 °C, while a similar 60% drop was measured for PLZT (9.0/65/35).