Waveguide instability in LiTaO3

The issue of waveguide instability in LiTaO3 is addressed. Changes in refractive index over time were monitored and used to compare the stability of waveguides fabricated by proton exchange, annealed proton exchange, Ti indiffusion, and Zn indiffusion. As opposed to waveguide formation in LiNbO3, all processes were found to produce unstable waveguides in LiTaO3 crystals. It was concluded, therefore, that to eliminate completely the instability of waveguides fabricated in LiTaO3 by using common fabrication techniques better growth procedures for this crystal may be necessary. Because of its extremely high melting point, current growth technology results in Li-deficient crystals that likely have a large number of defect sites and high strain values. (C) 2002 Optical Society of America.