Second-harmonic generation to green using ultrafast fibre source and femtosecond written periodically poled waveguide

The rapid fabrication of a periodically poled waveguide in potassium titanyl phosphate crystal using tightly focused femtosecond laser pulses, and utilised for second-harmonic generation to the green by an all positive dispersion ytterbium-fibre laser-amplifier, is demonstrated. A maximum average SHG power of 104.4 mW was measured for the 10 mm-long waveguide under optimal singlemode propagation. A conversion efficiency of 47.4% can be achieved.