Damage-resistant LiNbO3 waveguides

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Abstract
The photorefractive effect (‘‘optical damage’’) severely limits the application of LiNbO3 in visible wavelengths. We have found that proton exchanged LiNbO3, in which up to 70% of the Li ions are replaced by protons, exhibit no measurable index change with average intensities of visible light up to 5 kW/cm2 or peak pulse intensities of ∼5×108 W/cm2 in the guide. These experiments demonstrate that the photorefractive sensitivity of proton exchanged waveguides is at least four orders of magnitude lower than that of conventional titanium diffused guides. Similar results are obtained with titanium diffused waveguides which are subsequently proton exchanged.