Mechanism for efficient blue second-harmonic generation in periodically segmented waveguides

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Abstract
We present a theoretical investigation of the mechanisms responsible for the recently reported efficient type I blue second‐harmonic generation in periodically segmented KTiOPO4:Rb,Tl waveguides. In these guides, grating‐assisted phase matching of second‐harmonic light between 390 and 480 nm has been achieved. 5‐mm‐long guides give output powers on the order of 1 mW at around 425 nm with fundamental powers in the 50–100 mW range. We show that such high efficiencies can be expected from strongly perturbed guides through terms representing the modulation of phase mismatch and mode size in addition to the nonlinear susceptibility and refractive index modulations.