Structural phase transitions during annealing of proton-exchanged layers in X-cut and Z-cut lithium niobate

摘要

Phase transitions during annealing of proton-exchanged (PE) layers in X-cut and Z-cut lithium niobate (LN) crystals were studied. The following sequence of phase transitions is proposed: beta(1), beta(2)-phases -> kappa(2)-phase -> kappa(1)-phase -> alpha-phase. Main feature of kappa(2)-phase -> kappa(1)-phase transition in X-cut LN is the formation of particles of kappa(1)-phase, which create a modulated structure. In case of Z-cut LN, the particles of kappa(1)-phase do not arise and PE-waveguide consists of coherent layers until they completely transform into alpha-phase.