High spatial resolution interferometric analysis of internal field in lithium niobate (LiNbO3)

Lithium niobate is a material of great interest for both fundamental science and applications because of the richness of its physical properties. On periodical structured lithium niobate is based quasi-phase-matching technique that allows efficient conversion in nonlinear optical processes. A critical step is the ability to engineering ferroelectric domains on micrometer-scales necessary for the desired interaction. Many efforts have been made to achieve a good control of domain reversal process and to this aim become fundamental to study all effects that influence ferroelectric domains inversion. Among these lithium niobate internal field earns great importance because on it depends observed difference between electric fields required for switching ferroelectric polarization in opposite directions. Moreover it's time-temperature dependent and this feature can bias the stability of LiNbO3 based devices. We perform high spatial resolution interferometric measurement of internal field in lithium niobate crystals. In this way we can analyse influence of micrometer size not homogeneous area on internal field values. The samples are mounted in one arm of a Mach-Zehnder interferometer in microscopic configuration: resulting fringes patterns are visualized and stored by a CCD camera, then recorded data are processed by digital holographic technique in order to obtain 2D phase map of the sample with desired spatial resolution