Ridge Waveguides and Y-Branch Beam Splitters in KTiOAsO4 Crystal by 15 MeV Oxygen Ion Implantation and Femtosecond Laser Ablation

We report on the fabrication of ridge waveguides and Y-branch beam splitters in KTiOAsO
₄
nonlinear optical crystal by the combination of 15 MeV oxygen (O
⁵⁺
) ion implantation and femtosecond laser ablation. Guiding properties were investigated at the wavelengths of 633 and 808 nm, respectively, showing high polarization sensitivity of light propagation. Splitting ratios of these beam splitters are dependent on in-coupling alignment. The simulated guiding modal distributions of splitted guided beams, which was based on a reconstructed refractive index profile, shows reasonable consistence with the measured ones. After the stepwise annealing treatment at 473 and 573 K for 1 h each, the propagation losses for these guiding structures have been reduced considerably.