The photorefractive effect in titanium indiffused lithium niobate optical directional couplers at 1.3 µm

In titanium indiffused lithium niobate directional couplers, photorefractive damage is seen at a wavelength of 1.3 μm when power levels in the guide exceed 25 mW ( 5 \times 10^{4} W/cm 2 ) with time constants on the order of 100 h. Damage is not observed at lower power levels. Using a theoretical model based on the coupled wave equations and extrapolating the high power results, no significant degradation in performance is predicted for devices with less than 5 mW coupled into the waveguide.