Periodically Poled Nonlinear Photonic Crystal KTa_0.51Nb_0.49O₃ Combining Wide Transparent Range and Large Quadratic Coefficient

Abstract Since the first proposal of quasi‐phase‐matching (QPM) in 1962, finding new nonlinear photonic crystals has been an attractive topic in nonlinear optics fields. However, combining high conversion efficiency and wide operation range concurrently into one single crystal remains a great challenge. Herein, a periodically poled KTa_0.51Nb_0.49O₃ (PPKTN) is fabricated as a one‐dimensional nonlinear photonic crystal for the first time, to the authors’ best knowledge. Benefitting from the large quadratic nonlinear coefficient, the QPM second harmonic generation (SHG) at 1030 nm is realized with a high conversion efficiency of up to 39%. More importantly, KTN crystal possesses wider mid‐infrared spectral transparency (0.4–8.0 µm) than commercialized LiNbO₃ and KTiOPO₄. A 5 µm SHG is first achieved with a conversion efficiency of 6.3%, indicating that it is a promising candidate for broadband mid‐infrared parametric conversion. This work promotes PPKTN as a new nonlinear photonic platform to achieve highly efficient optical waveguide, holography, information storage, and all‐optical chips.