Broad-Band Second-Harmonic Generation in LiNbO3 Waveguide Using Optimized Domain-Inverted Grating

We demonstrate broad-band second-harmonic generation in a quasi-phase-matched LiNbO3 waveguide, with a window bandwidth as large as 13nm and a conversion efficiency up to 29%/W. Such a large bandwidth is achieved using an aperiodic domain-inverted grating structure optimized by simulated annealing.