Strontium titanate waveguide in visible and near-infrared regions induced by swift heavy Ni-ion irradiation

Abstract

In this work, the waveguide formation mechanism and related optical properties in strontium titanate crystal irradiated with 357 MeV Ni-ion at a fluence of 5 × 1013 cm−2 have been studied. The electronic energy loss along the swift heavy ion penetration path could produce lattice damage based on the inelastic thermal spike model, and therefore modify the refractive index distribution and further induce a waveguide formation. Irradiation damage behavior in the near-surface region has been analyzed by Rutherford backscattering spectrometry in a channeling direction. Optical properties of the prepared strontium titanate waveguide at visible and near-infrared wavelengths, including the guided mode, near-field intensity distribution and transmission loss, have been characterized by prism and end-face coupling measurements. Due to the relatively deep penetration of the swift heavy ions, the formed waveguide structure could effectively support multi-mode and single-mode transmissions in the visible and near-infrared regions, respectively. Utilizing the measured effective refractive indices of guided modes, the refractive index profile of the irradiation region has been reconstructed by the inverse Wentzel-Kramers-Brillouin method, further proving that the electronic energy loss induced by swift heavy ion irradiation plays a dominant role in the formation of strontium titanate waveguides.