High power blue laser source on the basis of frequency converted 1.3μm Nd-lasers

Up to 0.75 Watt of blue laser light have been generated by second harmonic generation and additional sum frequency mixing of a 1.3μm actively cw-modelocked Nd:YAG laser oscillator. Special attention has been paid to the design of the fundamental mode resonators, delivering output powers of up to 8W at the fundamental wavelength with nearly diffraction limited beam quality. To overcome the thermally induced depolarising birefringence a compensation scheme has been applied for further enhancement of the laser power.