Refractive index tailoring in congruent Lithium Niobate by ion implantation

Refractive index profiles of ion-implanted Lithium Niobate waveguides are investigated. Z+ and z− congruent Lithium Niobate samples have been implanted with C3+ ions at a fluence of 4 × 1014 ions/cm2. Dark m-lines measurements have been performed on ordinary (no) and extraordinary (ne) indexes for three different wavelengths (532 nm, 632.8 nm, 818 nm) before and after the annealing process. A reconstruction of refractive index profiles by Reflectivity Calculation Method (RCM) is presented and commented. The literature data for nuclear damage regime have been collected and critically examined. no and ne curves as function of the density of energy released in nuclear collisions, Ed, describing the effects of ion implantation on LN refractive indexes has been obtained on the basis of literature data. no depth profile, predicted according to no(Ed) curve, is in good agreement with the RCM reconstructed one. In the case of ne, a satisfactory agreement has been reached only slightly modifying the ne(Ed) curve and considering an alternative RCM profile structure.