Fig. 1. Schematic illustration of the phase-matching process and the simulations. (a) Theoretical principle of the proposed SHG in the LN slab waveguide. (b) Simulated evolution of the electric field in the waveguide at the SH frequency, indicating an efficient SHG process. The grating distributed region is emphasized with the pink box. (c) Simulated SHG intensity versus propagation length with different incident angles θ. (d) Simulated sinc2-dependence of the SHG on the incident angle.

Fig. 2. Experimental demonstration of the SHG in the slab waveguide. (a) SEM images of the fabricated samples with Ag cladding. (b) Schematic illustration of the measurement setup. (c) Measured SHG power at the output port of samples with different lengths of the coupling regions, in comparison with the simulations. (d) Quadratic power dependence between the pump and the SH signal in the experiments.

Fig. 3. Manipulation of SHG guided wave. Zoomed SEM images of structures for (a) an ordinary plane wave, (b) a focal lens, (c) a dual-focus lens, and (d) an Airy beam generator in the waveguide. (e)–(h) Measured light spot intensity profile coupling out from the facet of waveguides for four different beam manipulations. (i)–(l) Corresponding vertical cross sections of the light spots (black solid curves), in comparison with the simulation results (red dashed curves).