Influence of selective proton exchange on periodically poled lithium niobate

Abstract: The purpose of the present thesis is to study the influence of Proton Exchange on Electric Field assisted Poling of congruent Lithium Niobate and its applications on periodically pat-terned structures. Moreover, the possibility of using Proton Exchange to avoid neighbours domains merging is studied and successfully demonstrated for period shorter than 10μm. Before approaching the poling of periodically patterned LiNbO3 samples, the main charac-teristics of the evolution of the poling of uniform samples in different masking conditions are investigated. It is well known that the kinetics of domains switching is highly dependent on the poling setup and on the quality/type of electrode employed to contact the crystal to the high voltage. We used a thin layer of Titanium both as mask for proton diffusion and as metal electrode for poling experiments. Moreover different masking configurations are pre-sented and characterized. The second part of this work deals with the periodic poling of 0.5mm-thick congruent lith-ium niobate. 9x4 mm2 1-D Ti gratings with 8.66μm and 8.03μm period were first fabricated on the +z side of the crystal and a superficial chemical pattern was reproduced via acid bath. Three different types of samples were obtained and before the poling the metallic mask was removed whereas in one configuration it was left assuring better homogeneity of the in-verted areas. The results we obtained suggest it could be possible to achieve periodically poled congruent lithium niobate gratings with period shorter than 4μm in ~500μm thick samples and hence obtain aspect ratios of more than 250.