Fabrication And Application Of Optical-damage-resistant Near-stoichiometric Zr:Ti:PPLN Strip Waveguide

The lithium niobate crystal have good electro-optic,piezoelectric,non-linear optical properties.At the same time,it has low transmission loss in visible and near-mid-infrared bands.Periodically polarized lithium niobate?PPLN?based on quasi-phase matching technology has been widely used in frequency doubling,difference frequency,optical parametric oscillation and THz wave generation,which has become a research hotspot in the field of integrated optics.However,the photorefractive damage of the same component lithium niobate crystal in visible and near infrared bands hinders its application in the field of integrated optics.The Near-stoichiometric Zr:Ti:PPLN stripe waveguide has excellent optical-damage resistance,low transmission loss and lower voltage domain inversion.In this thesis,the near-stoichiometric Zr:Ti:LiNbO₃ strip waveguide were fabricated and periodically polarized.The fabrication of near-stoichiometric Zr:Ti:PPLN waveguide were completed.Furthermore,a THz wave generation system based on near-stoichiometric Zr:Ti:PPLN strip waveguide is designed,which provides a basis for further fabrication of THz high power transmitter based on photorefractive PPLN.The main research work in this thesis includes the following aspects:1.Fabrication and characterization of Zr doped Ti diffused planar waveguide with the congruent composition.The Zr:Ti:LiNbO₃ planar waveguide with the congruent composition were fabricated by Z-cut lithium niobate plate.The composition of the surface and the corresponding modes of TE and TM polarization at 1311 nm were measured,which lays the foundation for better preparation of Zr:Ti:PPLN strip waveguide.The composition of the waveguide surface is characterized,and the modes of TE and TM are measured at 1331nm and 1553nm wavelengths.Sellmeier equation is used to calculate the lithium oxide composition on the waveguide surface,which lays a theoretical and experimental foundation for better preparation of Zr:Ti:PPLN strip waveguide.2.Performance comparison of Zr:Ti:LiNbO₃ strip waveguide and Ga:LiNbO₃ strip waveguide.Zr⁴⁺and Ga³⁺have excellent optical-damage resistance,so Ga:LiNbO₃ and Zr:Ti:LiNbO₃ were fabricated and compared before fabricating near-stoichiometric Zr:Ti:PPLN.Then,the zirconium-doped titanium-diffused lithium niobite strip waveguide with the congruent composition were selected to achieve near-stoichiometric composition through lithium-rich VTE process.3.Fabrication and characterization of near-stoichiometric Zr:Ti:PPLN strip waveguide.By using the liquid electrode polarization system at 4.2 kV high voltage by polarizing 0.8s,near-stoichiometric Zr-doped Ti-diffused periodically polarized lithium niobate?NS Zr:Ti:PPLN?waveguide were successfully fabricated.The surface of the waveguide was observed by etching method and the domain period was 7.9?m.4.Design of THz emitter system based on NS Zr:Ti:PPLN strip waveguide.In the proposed scheme,780 nm laser is used as pumping light and 1550 nm laser as signal light,and 1570 nm idle light is generated by differential frequency of NS Zr:Ti:PPLN waveguide.Afterwards,the difference frequency generation of 1570nm and 1550nm light waves is THz wave near 2.47THz.It provides an important reference for further fabrication of terahertz high power transmitter based on optical-damage resistant PPLN.