Ti:LiNbO3 도파로 제작을 위한 열처리 과정 동안 강유전 도메인 특성에 미치는 영향

Abstract

It is demonstrated that the annealing process for Ti in-diffusion to z-cut LiNbO3 at temperature lower than the curie temperature in a platinum (Pt) box can cause a ferroelectric micro-domain inversion at the +z surface and Li out-diffusion, therefore which should be avoided or suppressed for waveguide type periodically poled lithium niobate (PPLN) devices. The depth of the inversion layer depends on the Ti-diffusion conditions such as temperature, atmosphere, the sealing method of LiNbO3 in the Pt box and crystal orientation is experimentally examined. The result shows that the polarization-inverted domain boundary appears at the only +z surface and its thickness is about 1.6mm. Also, for the etched LiNbO3 surface the domain shape was observed by the optical microscope and atomic force microscopy (AFM), and distribution of the cation concentrations in the LiNbO3 crystal by the secondary ion mass spectrometry (SIMS).