Buried channel waveguides in KTiOPO4 nonlinear crystal fabricated by focused He+ beam writing

Abstract We report on the fabrication of KTiOPO4 channel waveguides by using a new technique, i.e., focused He ion beam writing. With direct inscription of 2 MeV He+ beams of diameter of 0.5 μm, a local modified region with positive refractive index changes is created at the end of the He+ trajectory, constructing buried channel waveguides supporting both TE and TM polarizations. The calculated modal profiles of the waveguides are in good agreement with the experimental near-field intensity distributions. The propagation loss has been determined to be as low as ∼0.7 dB/cm, exhibiting good guiding properties for diverse photonic applications.