Characterization and engineering of ferroelectric microstructures by interferometric methods

In the last years lithium niobate (LN) has become one of the most important optical material in optoelectronics and nonlinear optics for its large electro-optics and nonlinear optical coefficients. Ferroelectric materials are employed in several electrooptic, acousto-optic, and nonlinear optical devices, as modulator of light, beam deflector, optical frequency converters, or tuneable sources of coherent light for spectroscopic applications. Manipulation of ferroelectric domains into gratings, matrices, or other shapes is possible. Fabrication of new ordered microstructures in LN samples through domain engineering followed by differential etching has been developed recently for applications in the fields of optics and optoelectronics. These microstructures have a range of applications in optical ridge waveguides, alignment structures, V-grooves, micro-tips and micro-cantilever beams and precise control of the surface quality and topography is required of for photonic band-gap structures. Moreover engineering ferroelectric domains by an electrical poling technique represent a key process for the construction of a wide range of photonic devices. Therefore, a thorough understanding of material properties and of the poling process are crucial issues. We will show that interferometric approach based on Digital Holography can provide a very useful tool for investigation and characterization of materials and of the engineered structures.