Observations and theory of high-power butt coupling to LiNbO3-type waveguides

We report the study and observation of high-efficiency (greater than 60 percent) and high-power (13 mW CW and 27 mW, 5 μs 5 percent duty cycle pulse) butt coupling of diode lasers to indiffused LiNbO
3
-type waveguides. We verified the predictions of the existing coupling theory at previously unreported power levels, and present a novel theoretical explanation of the effect of multiple reflections on laser output and waveguide coupling. The theory predicts our experimental observation that the amplitude of the periodic variation of laser output with laser-waveguide separation distance is a nonmonotonic function of laser drive current. Our measurements also lead us to infer that the onset of optical damage in Ti:LiNbO
3
occurs at a CW power density of
4 \times 10^{5}
W/cm
²
in the 0.83 μm wavelength region.