Research On Photonic Integrated Basic Devices Based On Lithium Niobate Thin Film

Photonic integration plays an important role in optical network computing,such as multi-wavelength laser,optical switch and wavelength convertor,optical logic gates and other photonic functional devices integration.Optical microcavity and photonic crystal based on thin film are good structures for integrated optics.Lithium niobate dominates in the design of optical functional devices because of its excellent nonlinearity characteristics.In addition,due to the commercial development of lithium niobate thin film fabrication technology,it attaches more interesting towards the application of photonic integrated devices.We studied the phase matching conditions of type I and type II second-harmonic generation in lithium niobate thin film at 900 nm thick based on dispersion equation of lithium niobate thin film.The phase matching position of type I second-harmonic generation in lithium niobate film with different thicknesses was analyzed.The mode field distribution matching condition in thin film was studied.We also successfully generated a second-harmonic wave with pump laser at 1018 nm on a 900 nm thick lithium niobate film.We also analyzed the three conditions of frequency doubling in optical microcavity in lithium niobate thin film by different methods.The mode of the lithium niobate microcavity was calculated by the coupled mode theory between waveguide and cavity.The effective refractive indices of lithium niobate thin film microcavity at different wavelengths were calculated by conformal transformation.Finally,we introduced the fabrication of lithium niobate thin film microcavity,which provides the theoretical basis and experimental preparation for the design of multi-wavelength laser based on lithium niobate thin film microcavity.Based on the two-dimensional lithium niobate pillared photonic crystal,we designed a novel all-optical gate and half-adder combined with photonic crystal defect waveguide and defect microcavity.By designing the defect microcavity to improve the waveguide beam splitting,we achieved a new all-optical gate with a maximum extinction ratio of 23 dB.The all-optical half-adder was designed based on the basic logic gates mention above,and through this way we realized the basic logic operation successfully.We provide an efficient realization scheme for the all-optical gate in the lithium niobate integrated optical chip.