Abstract
In the thesis, we proposed and experimentally demonstrated an optimized hyperfine aperiodic optical superlattice (HAOS) for the third-harmonic generation (THG). The HAOS outperforms the sequentially periodic structure in the conversion efficiency and the degree of freedom of achievable wavelength. We also discussed the several schemes to achieve third-harmonic generation by QPM technique, and the practical issue in fabrication. Finally, a three-section structure is proposed to exceed the maximum THG efficiency obtained by sequentially periodic method with two first-order QPM gratings which has the highest THG efficiency to the best of our knowledge.