Fabrication And Research Of Ion Implantation MgO: LiNbO₃ Planar And Channel Waveguide

Since the notion of integrated optics has been proposed by Bell Lab in 1960s, it greatly promote the development of optical communication, it is also the basic of full optical communication and calculation. Integrated optics is a combined system of photon and electron which based on the waveguide phenomena, connected by optical fiber and waveguide. The elemental components are waveguide devices. Using the theory that light will totally reflect in the interface of material with different refractive index, light wave propagation is confined in micron dimension film. The contents of integrated optics are extremely abundant, but the very foundation is light transmission in films. All the processing of light signals must depend on light wave propagate in films. Thus, waveguide play a crucial role in integrated optics. Therefore, people apply various technologies to fabricate waveguide.Ion implantation has following merits comparing to other methods such as diffusion and exchange: it can change the refractive index of materials without changing the materials' optoelectronic properties and has little damage on crystal structure of waveguide layer; it can process in relatively low temperature; and we can precisely control the dose and depth of implantation.Ion implantation includes two methods, one is light ion implantation and the other one is a new method called low dose heavy ion implantation. Heavy ion implantation has following advantages: the dose of ions is very low and two or three magnitude orders lower than light ion implantation which can reduce implantation time considerably and lower the fabrication cost consequently; the damage layer of heavy ion implantation is beneath the crystal surface about 1um to 1.5um which can easily form single mode waveguide.Lithium Niobate (LN) is widely and most frequently used for preparation of variety of waveguide devices due to its large optoelectronic, opt acoustic and nonlinear coefficients and stable chemical capacities as well as low cost to grow big single crystals. It has important applications in the fields of single mode fiber communication systems, signal processing and sensors etc. This artificial crystal is as valuable as silicon crystal.Lithium Niobate has such versatile properties and promising applications also closely relate to its numerous doping elements. Pure lithium Niobate provide us a good platform, various dopant make this crystal so important. Of which high doped magnesium (over 4.6%mol), photorefractive resistance ability improve in two magnitude orders. MgO: LiNbO₃'s high resistance to optical damage meets to the application requirement of high power density devices such as modulator, frequent doublers and waveguide laser resonator. To fabricate and further investigate the optical and structure characters of MgO: LiNbO₃ ion implantation waveguide has an important value in broaden the application areas of waveguide devices. Therefore, we mainly use magnesium doped lithium niobate (MgO: LiNbO₃) as experiment materials.Conventional waveguide preparation methods for LN such as Ti diffusion and proton exchange meet several difficulties when apply to MgO: LiNbO₃. Using Ti diffusion method, both the diffusion coefficient and photorefractive resistant ability will decrease. Using proton exchange method, the diffusion speed will slow down. Moreover, waveguide made by these two methods has a comparably large propagation loss. Due to the advantage of ion implantation method, it might become an effective approach to make low loss MgO: LiNbO₃ waveguide.We did research on Z-cut MgO: LiNbO₃ samples implanted by low dose O²⁺ ions. Firstly, we made MgO: LiNbO₃ planar waveguide with implantation energy from 1.5MeV to 4.5MeV and implantation dose from 4×10¹⁴ to 12×10¹⁴ions/cm². Single mode waveguide was formed by increased extraordinary refractive index at TM polarization of wavelength of 633nm and 1539nm respectively. The change of waveguide loss and refractive index profile followed by different annealing treatments were observed and measured. After annealing at 230℃and 30miniutes, the propagation loss of the waveguide was down to 0.9dB-2.0dB.Research on fabrication of MgO: LiNbO₃ channel waveguide was introduced. Both single energy and multiple energy ions were implanted into samples with stripe patterned metal mask to make channel waveguide. The implantation parameter of single energy is 1.5MeV and 3.5MeV with same implantation energy 6×10¹⁴ions/cm², while 3.0MeV+3.6MeV+4.5MeV and totally implantation dose of 8.8×10¹⁴ions/cm² The samples of multiply energy implantation and 3.5MeV implantation formed low loss single mode waveguide with TM polarization at wavelength of 1550nm which is the fiber communication wave band. For multiple energy implantations, the measured propagations lie mainly between 0.38-0.45dB/cm, the value matches the requirement for practical application (smaller than 1dB/cm).This thesis systematically researched on fabrication of MgO: LiNbO₃ channel and planar waveguide using oxygen ion implantation. The change of sample's optical properties formed by different implantation parameters was analyzed. The effects of different annealing parameters for refractive index and waveguide loss were discussed. All the data and analysis provide rich experimental basis for fabricating low loss MgO: LiNbO₃ waveguide devices.