Anisotropic Focusing Characteristics of Micro - domain Structures within Crystalline Sr Ba Nb O : The Crystal Ball

We report the anisotropic focusing characteristics of a spherically configured region of micro-domains that have been induced within a cubic shaped crystal of Ce:doped Sr Ba Nb O . The internal spherical structure 0.61 0.39 2 6 focuses extraordinary polarised light, but not ordinary polarised. The spherical region, which is easily observed via scattering, is formed as the crystal cools down, after a repoling cycle through the Curie temperature, with an applied field. Analytic modelling of the thermal gradients that exist within the crystal during cooling reveals a small (<1 ) temperature difference between the central and outside regions. The similarity in shape between o these temperature profiles and the observed scattering region suggests a possible mechanism for the growth of this spherical micro-domained structure.