Low-loss optical planar waveguides in Li2B4O7 crystal formed by He+ implantation

Formation of planar waveguide in lithium tetraborate (Li2B4O7) crystal by 2 MeV helium (He+) implantation is reported. Investigation of the induced de fects is performed by using a modified m-lines setup. Results indicate that the optical properties of the guiding core are not affected by the implant ation process. Moreover the produced defects are shown to be isotropic and localized at the optical barrier position without any extension towards the surface. Optical losses measured by using a new approach are found to be l ess than 2 dB cm(-1). Finally the influence of postannealing procedure appl ied to the sample showed a stability of the optical properties of the guide with 10% improvement of optical losses. (C) 2001 American Institute of Phy sics.