Ultrafast generation of blue light by efficient second-harmonic generation in periodically-poled bulk and waveguide potassium titanyl phosphate

We have investigated second-harmonic generation in short-period periodically-poled bulk and waveguide potassium titanyl phosphate crystals to generate blue light using subpicosecond laser pulses. For the bulk, the highest conversion efficiency is $\text{≈5.5\%,}$ which is about two orders of magnitude larger than that achieved previously. For the waveguide, the highest conversion efficiency is $\text{≈32\%,}$ which is about a factor of 4 higher than that obtained before. These measured values are in good agreement with our theoretical results. We have observed saturation of conversion efficiency, which sets a limit to the maximum efficiency that can be achieved.