A comparison of optical damage in different types of LiNbO3waveguides

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Abstract
A comparative study is presented of the optical damage induced by green light in LiNbO3 waveguides prepared by Ti in-diffusion, proton exchange and ion implantation. The methods used were monitoring the out-coupled light power as a function of time and as a function of in-coupled power, and writing and erasing a holographic grating inside the guide. With the first method, the optical damage stability of Ti-diffused guides is greatly inferior to the other two types, optical damage appearing at in-coupled intensities of 6 W cm-2 in Ti-diffused guides but not until 500 W cm-2 in exchanged and implanted guides. With the holographic method, however, a similar photorefractive behaviour is observed for diffused and implanted guides which contain similar levels of Fe2+ impurities, whereas much less damage is apparent in proton-exchanged guides. Main photorefractive parameters are given for the three types of guides and their physical implications briefly discussed.