Potassium niobate waveguides: He+ implantation in bulk single crystals and pulsed laser deposition of thin films

We present a new mask design and implantation scheme, which uses a single ion implantation step of 2 MeV He ions at a dose of 7×1014 to 3×1015 He cm−2 to form channel waveguides in single crystal KNbO3. The special processing of the photoresist mask enables the formation of channel waveguides with a trapezoidal-shaped cross section, providing for the first time simultaneous confinement of both TE and TM modes in a permanent KNbO3 channel waveguide. Second-harmonic blue light (2.6 mW) at 441 nm was generated in a 5.8 mm long guide for a fundamental power of approximately 200 mW. In the second part of the paper, we demonstrate the deposition of single crystal KNbO3 films on SrTiO3 and BaTiO3/MgO substrates by Pulsed Laser Deposition (PLD). Technologically interesting optical materials such as BaTiO3 and KNbO3 are difficult to grow as single crystals of large dimensions. Thin film techniques can overcome this problem by synthesizing these materials on commercially available substrates.