Search

The dependence of propagation losses on waveguide width and polarization is measured for strip and rib waveguides made of tantalum pentoxide. For strip waveguides, the propagation losses are found to increase rapidly for widths <;3 μ m. The losses were significantly smaller for rib than for strip waveguides, as expected. A method is developed for estimating the dependence of propagation losses on waveguide width. The method is based on approximating sidewall imperfections with an area with complex refractive index in a 2D model and showed a good agreement with the measured dependence on waveguide width. The method is also used to predict that propagation losses will decrease rapidly for rib heights less than 20 nm for TM-polarization. [ABSTRACT FROM PUBLISHER]

We report a Ti:Er:LiNbO3 strip waveguide with high diffusion-doped surface Er3+ concentration. The waveguide was fabricated with a technological process in sequence of preparation of noncongruent, Li-deficient LiNbO3 substrate by performing Li-poor vapor transport equilibration treatment on a congruent Z-cut LiNbO3 plate, diffusion of 40-nm-thick Er metal film, and fabrication of 8-μm-wide Ti-diffused strip waveguide. The waveguide retains the LiNbO3 phase and shows the waveguiding characteristics similar to the conventional Ti:LiNbO3 waveguide. Secondary ion mass spectrometry study shows that the Er3+ diffusion reservoir was exhausted and the profile is Gaussian with a surface concentration two times larger than that of the conventional Ti:Er:LiNbO3 waveguide. The waveguide shows stable 1547-nm small-signal enhancement under the 1480-nm pumping without serious optical damage observed, and a 5-dB signal enhancement is obtained for the available coupled pump power of only 90 mW. A saturated net gain as much as 5 dB/cm is predicted theoretically. [ABSTRACT FROM PUBLISHER]