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Lithium niobate crystal is a good nonlinear optical crystal material, it has excellent optical, ferroelectric, electro-optical, optical, photorefractive and other properties, the optical waveguide structure was prepared in the lithium niobate on the basis in the optical communication, the optical fiber sensing, optical instruments, optical information processing and optical computing has an important purpose. Fabricate waveguides as an effective new technology, ion implantation has attracted extensive attention. It can change the refractive index of the material, and does not substantially change the photoelectric characteristics of the material, and small influence on the the crystal waveguide layer structure, can be carried out in the lower temperature, the implantation dose and depth can be accurately controlled. So far, it has been formed a large number of optical materials including optical crystal, glass, semiconductor, and an organic polymer, including an optical waveguide structure using ion implantation technique. Ion implantation of lithium niobate waveguide since the beginning of the seventies of the 20th century, researchers initially injected with high doses of light ions of lithium niobate, are mainly used for ions, such as He, H injected dose 10 16 < / sup> magnitude, typically multi-mode waveguide is formed. The mechanism is damaged layer is formed, the end of the range of the ion implantation crystal lattice portion amorphous damage layer and the density is reduced, causing the injury had the refractive index is decreased, to form a light degree barrier, the light is limited to the barrier and the surface of the light degree the spread of the region surrounded by the air layer, this area becomes the waveguide structure. Later, the heavy ions is used to inject the lithium niobate to form a waveguide structure, the report mentioned heavy ion O ions, C ions, Ni ions, Si ion and the like. Spectroscopic ellipsometry is a commonly used method of measuring material surface properties, optical properties and thickness of the thin film material is obtained by analysis of the change in polarization state of the polarized light at the film sample under test before and after the surface reflection. Measuring the initial state and final state, the use of polarized light system Jones matrix or Mueller matrix can determine study material transformation of polarized law. The method because of its unique advantages is widely used in various fields of physics, chemistry, materials science, biology, and optical, electronic science. This article describes the basic principles of the reflective ellipsometry derive several different film ellipsometric parameters of the model. Effect of different dose, B ions and Ni ions of different energy levels into the Z-cut lithium niobate optical polishing wafers and not subjected to ion implantation of the lithium niobate wafer, measurement of the single crystal nature of the crystals of lithium niobate and ion implantation and transmittance. Experiments show that after the two ion-implanted into the lithium niobate crystal, still retain a good monocrystalline nature and doping the lattice damage caused by small, with a basic condition is applied to the optical waveguide. Measured after ion implantation with a reflection-type spectral ellipsometry, lithium niobate ellipsometric parameter to study the relationship between the layered homogeneous anisotropic multilayer film ellipsometric parameter and each film refractive index and thickness of the transcendental equation . SRIM software simulation of the ion implantation process, the simulated curve of the damage caused by ion injection after crystal crystal injection range at 2.0μm nearby, less damage to the injected B ions, the largest atomic substitution rate of 23.1%; injection Ni ions crystal injection shallower depth of 1μm, greater damage, the largest atomic substitution rate was 55%. According to the simulation results of the lithium niobate waveguide model obtained model corresponding ellipsometric formulas, computer programming 0.3μm ~ 0.8μm band waveguide and the refractive index of the damage zone dispersion fitting formula. The results show that the ion implantation unusual light with abnormal light dispersion curves remained the original shape of the four parameters corresponding change in the refractive index dispersion formula, light damage zone unusual extraordinary index has fallen markedly, waveguide region The refractive index is greater than the damage zone, and thus the light can be limited to be propagated in the waveguide region. The research results have important applications of lithium niobate crystal waveguide.
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