Low-loss optical channel waveguides in KNbO3 by multiple energy ion implantation

Permanent optical channel waveguides in single crystals of KNbO3 are formed with low-dose MeV He ion irradiation. A single energy implantation forms a confinement barrier at the projected range of the ions whereas multiple energy implantations combined with a positive shielding mask form the side walls. Guiding modes are produced and propagation losses as low as 1.0 dB/cm are measured without the need for any annealing. The irradiation induced refractive index changes that define the boundaries of the waveguiding channels are made visible with cross-polarized light microscopy.