Generation of 1.2 W green light using a resonant cavity-enhanced second-harmonic process with a periodically poled KTiOPO4

We report on frequency doubling of a single frequency cw Nd:YAG laser at wavelength of 1064 nm using a periodically poled KTiOPO4 crystal (PPKTP) placed in a single resonant ring enhanced cavity. A maximum output power of 1.23 W, corresponding to 72% of conversion efficiency with 1.7 W of fundamental power, was achieved. This is, to the best of our knowledge, the highest power obtained at this wavelength with PPKTP crystal in an external enhanced cavity. The output power is continuously stable with a peak to peak fluctuation of less than 1% over 4 h owing to optimum design of an enhanced cavity; moreover, the setup is inherently simple and robust. Therefore, it is suitable to be a light source for quantum optics experiments.