Refractive index profiles in LiNbO3 waveguide formed by 3.2 MeV He ions

Optically polished y-cut LiNbO3 was implanted at 3 x 10(16) ions/cm(2) at r oom temperature. In order to minimize any channeling effects, the sample wa s implanted at 7 degrees off the major symmetry axis. The He beam current w as approximately 700 nA and the scanning area was 0.8 cm(2). The prism coup ling method was carried out to measure the dark modes in the LiNbO3 wavegui de. In the present work, an isosceles prism (rutile) was used. The dark mod es were measured at 632.8 nm (He-Ne). Fifteen TM modes and 13 TE modes in t he LiNbO3 waveguide were observed. We have used the reflectivity calculatio n method (RCM) developed by Chandler and Lama to fit the refractive index p rofile. This method has been used for ion-implanted waveguides based on dar k mode lines by the prism coupling method. Also we have used the TRIM (tran sport of ions in matter) code to simulate the damage profile in LiNbO3 by 3 .2 MeV He ions which is helpful for choosing the analytic function in RCM c alculations. (C) 2000 Elsevier Science S.A. All rights reserved.