Broadband frequency tripling in locally ordered nonlinear photonic crystal.

We propose and fabricate a LiNbO₃-based nonlinear photonic crystal with locally ordered ferroelectric domains. The nonlinearity modulation provides sets of uniformly distributed reciprocal lattice vectors, ensuring broadband high frequency conversion efficiency. Frequency tripling via cascading is demonstrated in the range of 1400-1830 nm, with energy conversion efficiency up to ∼15%.