Efficient frequency doubling in femtosecond laser-written waveguides in lithium niobate

Optical waveguides in lithium niobate have been fabricated with a femtosecond laser. Different types of modifications depending on the laser parameters were observed and discussed. In these waveguides, frequency doubling of 1064 nm radiation was demonstrated utilizing birefringent phase matching. A conversion efficiency of 49% was obtained in a 9.3 mm long sample.