摘要： Lithium niobate (LN) is a favourable material for many applications, especially in integrated optics, due to its excellent electro-optic, acousto-optic, and nonlinear optic properties. One promising application of LN is second-harmonic generation (SHG). For enhancing the efficiency of SHG, phase matching between the interacting waves is needed, which is often realized by employing quasi-phase matching (QPM). QPM is typically realized by periodic poling of LN, i.e. the periodic flipping of the crystal orientation. The needed period is determined by the wavelengths as well as by the wave vectors of the fundamental- and the second-harmonic waves (FW and SH, respectively). For the case of backward SHG with a fundamental wavelength of 1.55 μm, where the SH wave travels in the opposite direction to the FW, typically sub-micrometer periods of the poled LN are required. Here, we demonstrate the realization of short-period QPM structures in LN-on-insulator (LNOI) thin-film substrates with a thickness of 600 nm. We aim to fabricate periodically poled LNOI (PPLNOI) waveguides with a periodicity as small as 1 μm, facilitating efficient nonlinear interaction due to the strong mode confinement.