Investigation On Preparation And Characteristics Of Waveguides In High-gain Neodymium-doped Laser Glass

In recent years,high-gain Nd³⁺-doped laser glass has been widely concerned,with the rapid development of optical communication technology and the wide application of laser technology.It has the advantages of long fluorescence lifetime,large stimulated emission cross-section and high optical uniformity.Therefore,it becomes an important laser material used in high-power laser systems.Waveguide is a key component in integrated optical devices,which affects the performance of optical devices and even the whole optical system.In the field of laser amplification,the fabrication of waveguide laser devices has become a hot research topic.The first premise of realizing waveguide laser device is to construct optical waveguide structure.In this thesis,the high-gain Nd³⁺-doped laser glass is used as the matrix material,and the planar and ridge waveguide structures are fabricated on it through various technologies.The optical guiding properties of waveguides are studied,which lays the foundation for the preparation of other Nd³⁺-doped laser glass waveguide devices.At the same time,a design scheme of 1057-nm waveguide laser output is proposed,according to the characteristics of Nd³⁺-doped phosphate laser glass waveguide.This thesis mainly includes the following aspects:Firstly,the characteristics of Nd³⁺-doped laser glass and its research status at home and abroad are discussed,and the research progress of Nd³⁺-doped glass waveguide devices is briefly introduced.Subsequently,the theoretical basis of optical waveguide is described,including waveguide structure,fabrication process and characterization methods of waveguide optical properties.Secondly,the high-gain Nd³⁺-doped laser glass planar waveguides are fabricated by ion implantation,and the optical properties of the waveguides implanted with H⁺and He⁺are discussed respectively.The process of ion implantation and the mechanism of waveguide formation was analyzed by the SRIM software.In order to evaluate the quality of planar waveguides fabricated by H⁺-and He⁺-ion implantation respectively,the dark mode curves of the waveguides were measured,the refractive index distribution was simulated by RCM,as well as the near-field light intensity distribution was observed at the wavelength of 633 nm emitted by He-Ne laser.The results show that the proton implantation with an energy of 400 ke V and a fluence of 8×10¹⁶ions/cm² can obtain near-field light intensity distributions before and after annealing.Besides,after annealing at 200?for 1h,it is found that the refractive index of the waveguide region tends to that of the substrate,which improves the damage induced by ion implantation and the optical transmission quality.Compared with the helium ion implanted waveguide with an energy of 400 ke V and a fluence of 6×10¹⁶ ions/cm²,the optical performance of the hydrogen ion implanted waveguide is better.Thirdly,two-dimensional ridge waveguides with ridge widths of 15?m,20?m,25?m and 30?m are appeared by femtosecond laser ablation and the 10?m wide ridge waveguide is cut by the precise diamond blade dicing technology,which are manufactured on the basis of the H⁺ion-implanted Nd³⁺-doped laser glass planar waveguides.An optical microscope objective was used to characterize the morphology of all waveguide structures prepared by different technologies.The mode propagation distributions for ridge waveguides with five different widths in the near infrared band of 976 nm were obtained,indicating that the two-dimensional ridge waveguides have good light guiding effect.Fourthly,the basic structure of the waveguide laser is introduced,and a compact Nd³⁺-doped phosphate glass waveguide laser is designed from the three aspects of pumping configuration,coupling manner and resonator selection.A laser pumping experiment platform is built according to the design scheme.