Visualization of κ1-phase in proton-exchange waveguides on the surface of lithium niobate crystal.

This work is devoted to the visualization and evolution of κ₁-phase particles in annealed proton exchange (PE) waveguides. It is well-known that the presence of κ₁-phase particles in optical waveguides leads to an increase in their optical losses and instability of operation. It has been found that precipitated κ₁-phase particles propagate through the whole waveguide depth and have perpendicular orientation to the surface of the lithium niobate crystal. These results are important for fast quality control of annealed PE waveguides. [ABSTRACT FROM AUTHOR]