KTiOPxAs1−xO4 optical waveguides grown by liquid phase epitaxy

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Abstract
We report on a new type of optical waveguide based on the nonlinear optical material KTiOPO4 (KTP). Thin films of KTiOPxAs1−xO4 (5–50 μm) were grown on KTP substrates by liquid phase epitaxy using a tungstate flux. Energy‐dispersive x‐ray spectrometry reveals an abrupt increase in the arsenic concentration in the film, suggesting an abrupt, step‐like refractive index profile in these guides. Optical waveguiding at 0.633 μm was demonstrated in a 20‐μm‐thick KTiOP0.76As0.24O4 film grown on a {011} KTP substrate. The refractive index difference between the film and the substrate (Δn) was measured to be ∼0.012, which compares favorably with the value estimated from bulk crystal measurements of the end members. Variations in the design of these waveguides and several potential applications are discussed.