Continuous-wave, high-power second-harmonic generation in laser-written PPLN-waveguides

We present recent progress in direct laser writing of waveguides in periodically poled lithium niobate (PPLN) crystals for nonlinear-optical frequency conversion. For pump powers below 2W, a conversion efficiency of 5.5 %/W is achieved for second-harmonic generation of 780-nm-light with an excellent beam profile. At higher pump powers, the conversion efficiency is reduced. Up to 2W of second-harmonic light are reported which is the first demonstration of Watt-class, continuous-wave frequency conversion in laser-written waveguide in PPLN.