LiNbO_3 waveguide second-harmonic-generation device phase matched with a fan-out domain-inverted grating

A LiNbO(3) waveguide optical second-harmonic-generation (SHG) device, consisting of a channel waveguide array and a ferroelectric domain-inverted grating in a fan pattern for quasi-phase matching, is proposed. The structure has redundancy to absorb the residual phase mismatch caused by design uncertainties and fabrication errors. A SHG device of 3-mm interaction length was fabricated by domain inversion by Ti indiffusion and channel waveguide formation by annealed proton exchanging and reactive ion etching. A normalized SHG efficiency of 17%/W was experimentally obtained for pumping by a cw Nd:YAG laser.