Effects of interference in quasiphase-matched periodically segmented potassium titanyl phosphate waveguides

We show that optical interference of two input beams coupled into a periodi cally segmented KTiOPO4 waveguide can increase the efficiency of the genera ted second harmonic by a factor of three over coupling a single beam with t he same total power. A simple model based on two interfering Gaussian beams indicates that the second harmonic output increases by enhancing the coupl ing of the fundamental energy into the waveguide. A Mach-Zehnder interferom eter scheme is used to demonstrate this effect. The variation of the second harmonic power with the fundamental input power of the interfering beams s hows excellent qualitative agreement between experimental results and the m odel presented. (C) 1999 American Institute of Physics. [S0003-6951(99)0314 7-2].