Formation of planar optical waveguides in the new nonlinear gadolinium calcium oxoborate, Ca4GdO(BO3)3, crystal by 2-MeV He+ implantation

A planar waveguide composed of the new nonlinear material, Ca4GdO(BO3)(3) (GdCOB), is reported. This crystal belongs to the calcium oxoborate family. It has attractive nonlinear properties that can be of great interest in integrated optics applications. We used a method of He+ implantation to fabricate waveguides in GdCOB crystals by creating a buried layer of lowered refractive index a few micrometers beneath the surface. Both TE and TM modes were observed. Therefore, according to the Y cut of the crystal, refractive-index values of n(x), n(y), and n(z) were obtained. Index profiles were reconstructed by an improved inverse WKB method. The profiles showed a steplike index behavior, indicating that the guiding region obtained was of good optical quality. (C) 1998 Optical Society of America.