Bi-layer optical waveguide formed by double boron ion implantation into strontium barium niobate crystal

We report a bi-layer optical waveguide in a Ce-doped strontium barium niobate (SBN) crystal formed by double boron ion implantation. The energies of the B+ and B3+ ions are 3 and 6 MeV, respectively, while the doses of the two boron implantation are both 2 × 1014 ions/cm2. A classic m-lines arrangement is performed to investigate the waveguide properties of the sample. The reconstructed refractive index profile of the waveguide shows a double-barrier confined shape, which suggests the formation of a bi-layer waveguide structure. The thickness of the two guide layers are 2.6 and 4.6 μm, respectively, which is in a good agreement with the mean projective range of the implanted boron ions of 3 and 6 MeV in the crystal. The nuclear energy loss distribution of the boron ions into SBN has a similar shape to that of the waveguide index, which means an inherent relationship between the waveguide formation and the energy deposition of the energetic ions.