Study On Ho-doped Ti:LiNbO₃ Waveguides And Related Material

Lithium niobate crystals have excellent optical and electrical properties and are excellent materials for optical waveguide devices.The main work of this paper is to investigate the diffusion and spectral properties of holmium ions in lithium niobate crystals.Holmium-doped titanium-diffused lithium niobate planar waveguides and strip waveguides,titanium diffused lithium tantalate planar waveguide and Holmium-zirconium co-doped titanium-diffused lithium niobate strip optical waveguides were fabricated and characterized.The work can be summarized as follows1.the diffusion properties of holmium ions in lithium niobate crystals were studied.According to the study on holmium-doped lithium niobate crystals,The results show that holmium doping does not cause changes in crystal composition and refractive index.According to the results of secondary ion mass spectrometry of holmium-doped lithium niobate crystals,The holmium ion concentration in the lithium niobate crystals follows a Gaussian distribution in the depth direction,and the diffusion and solubility coefficients of holmium ions are calculated according to the different diffusion conditions.The results show that it increases with increasing temperature.According to the Arrhenius theorem,the diffusion constants of holmium ions in lithium niobate were calculated and the activation energies were,respectively,3.78×10⁷?m²/h and 1.87eV,and the solubility constants,heat of dissolution were,3.03×10²⁶atoms/cm³,and 1.75eV,respectively.2.the spectral properties of holmium ions in lithium niobate crystals were investigated.The results show that when pumping holmium-doped lithium niobate crystals with a wavelength of 250nm,down-conversion fluorescence at 548nm and759nm was obtained.Down-conversion fluorescence at 617nm and 618nm was obtained respectively at excitation wavelengths of 336nm and 350nm.When pumping holmium-doped lithium niobate crystals using 540nm and 890nm wavelengths,a mid-infrared fluorescence of 1.67?m was obtained In general,the Holmium doped lithium niobate wafers are able to convert UV to visible light and also to emit mid-infrared light.3.Holmium-doped titanium diffused lithium niobate planar waveguides and titanium diffused lithium tantalate planar waveguide were prepared and characterized.The results show that according to the birefringence characteristics of the crystal,The calculated lithium oxide component of the holmium-doped titanium diffused lithium niobate planar waveguide is 48.0mol%,The lithium oxide component of the titanium diffused lithium tantalate planar waveguide is 47.46mol%.Using the prism coupling technique and the IWKB method to obtain the refractive index of the holmium-doped titanium diffused lithium niobate planar waveguide and titanium diffused lithium tantalate planar waveguide obey Gaussian distribution in the depth direction.The results of secondary ion mass spectrometry show that the concentration of titanium ions in the titanium diffused lithium tantalate planar waveguide follows Gaussian distribution in the depth direction,and the relationship between the refractive index change value and the concentration of titanium ions has polarization insensitivity and satisfies the exponential relationship.Different substrate materials have different relationships between the refractive index change value and the concentration of titanium ions.4.Single-mode titanium diffused lithium niobate strip waveguides were designed and simulated,and A Z-cut holmium doped titanium diffused lithium niobate channel waveguide was fabricated and characterized.The results showed that the single-mode titanium diffused strip waveguide can perform well for single-mode transmission at widths of 8?m and 10?m.the lithium oxide component in the waveguide and non-waveguide regions of the sample was 48.28 mol%and 48.23mol%,respectively,which remained the identical.The results of the secondary ion mass spectrometry experiment of the sample show that the concentration of holmium and titanium ions in the waveguide region obey a Gaussian distribution in the depth direction,and the concentration of titanium ions obey a distribution of two error function sums in the width direction.The waveguide can support single mode transmission under 1547nm light source,with TE and TM modes,and the transmission loss in TE and TM modes are 0.42dB/cm and 0.75dB/cm,respectively.5.A Z-cut holmium-zirconium co-doped titanium-diffused lithium niobate channel waveguide was fabricated and characterized.The results showed that the lithium oxide component in the waveguide and non-waveguide regions was 48.21mol%and 48.24 mol%,respectively.which remained the same,Therefore,zirconium doping does not affect the lithium oxide component of the waveguide region.The results of the secondary ion mass spectrometry experiment of the sample show that the concentration of Holmium,zirconium and titanium ions obey a Gaussian distribution in the depth direction,while the concentration of titanium ions in the waveguide region obey the distribution of two error function sums in the width direction,The diffusion depth of zirconium ions completely covers the diffusion depth of titanium ions,and the waveguide has the ability to resist photorefraction.The waveguide supports single mode transmission under 1547nm light source,with TE and TM transmission modes and the transmission loss in the TE and TM modes of the waveguide is 0.62dB/cm and 0.92dB/cm,respectively.Innovations in this thesis include:(1)Preparation of holmium-doped lithium niobate crystals by high temperature thermal diffusion method and the diffusion characteristics of holmium ions in lithium niobate crystals were studied in detail It was determined that the distribution of holmium ion concentration in holmium-doped lithium niobate crystals follows a Gaussian distribution and diffusion constants,activation energies,solubility constants and heat of dissolution were calculated.(2)the spectral properties of holmium doped lithium niobate fabricated by high temperature thermal diffusion method were investigated and the visible and mid-infrared luminescence were achieved.(3)For the first time,the preparation and characterization of holmium-doped titanium diffused lithium niobate planar waveguide,strip waveguide and titanium diffused lithium tantalate planar waveguide.(4)The holmium-zirconium co-doped titanium diffused lithium niobate strip optical waveguide was prepared for the first time,which provides a new field for the research of new active lithium niobate optical waveguide devices.