Photorefractive-Damage-Resistant Locally Er–Mg-Doped Near-Stoichiometric Ti : Mg : Er : LiNbO $_{3}$ Strip Waveguides: A Way Towa

We report photorefractive-damage-resistant near-stoichiometric (NS) Ti : Mg : Er : LiNbO₃ strip waveguides fabricated on an initially congruent, undoped Z-cut substrate in sequence by local Er-doping in air, Mg-Ti prediffusion in wet O₂ atmosphere, and post vapor-transport-equilibration. These waveguides with an initial Ti-strip width of 4-7 μm are single-mode at 1.3-1.5 μm, support only transverse-magnetic mode, and have a loss of 1.4 dB/cm. The waveguides are NS, still retain LiNbO₃ phase, and show stable 1531-nm small-signal enhancement under the 980-nm pump power of at least 216 mW, implying that the photorefractive effect is effectively suppressed. The waveguides would open up a way towards new devices.