Optical damage resistant Ti-diffused Zr/Er-codoped lithium niobate strip waveguide for high-power 980 nm pumping

Ti⁴⁺-diffused Zr⁴⁺/Er³⁺-codoped LiNbO₃ strip waveguide was fabricated on an X-cut LiNbO₃ substrate by thermal diffusion in sequence of Er³⁺, Zr⁴⁺ and Ti⁴⁺. Secondary ion mass spectrometry study shows that the Ti⁴⁺ ions follow a sum of two error functions in the width direction and a Gauss function in the depth direction of the waveguide. Both Er³⁺ and Zr⁴⁺ profiles follow the desired Gauss function, and entirely cover the Ti⁴⁺ profile. Optical study shows that the waveguide is TE or TM single mode at 1.5 μm wavelength, and has a loss of 0.3 (0.5) dB/cm for the TM (TE) mode. In the case of 980 nm pumping, the waveguide shows stable 1547 nm signal output under high-power pumping without optical damage observed, and a net gain of 1.1 dB/cm is obtained for the available pump power of 120 mW.