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

Changes in the refractive indices Delta n(1) and Delta n(3) Of clamped transparent relaxor ferroelectric (9.5/65/35) and (9.0/65/35) PUT ceramics were measured as a function of temperature ranging from -30 degrees C to 60 degrees 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 Delta 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 Delta n(1) with temperature remained unchanged and was independent of the DC field applied. The quadratic electro-optit coefficients of these two PLZT compositions were also obtained at 0, 20 and 40 degrees C, and a significant nonlinearity was observed: an 85% decrease in the electro-optic coefficient of PLZT (9.5/65/35) was measured at 40 degrees C compared to 0 degrees C, while a similar 60% drop was measured for PUT (9.0/65/35). Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.