Study Of The Cerenkov Type Second Harmonic Generation In Ion-implanted Lithium Niobate Planar Wavevguides

Optical waveguide is the base structure of integrated optics and the holo-optical network. Optical waveguide structures are of great importance for the application of the modern optical telecommunications. The specific properties of the waveguide have made waveguide play an important role in the fabrication of various optical devices. Because of its importance in practical application, many people are investigating the ways to fabricating "high-quality" optical waveguide. Recently the study of waveguide lasers and amplifiers has become one of the most interesting focuses in the integrated optics, while the necessary method for the waveguide laser generation is to form waveguide structures in the laser materials.Ion implantation has become one of the most promising techniques for the fabrication of various waveguides. Up to now, many waveguide structures have been formed by ion implantation in various materials such as optical crystals, glasses, semiconductors and polymers, etc. Nowadays the ions with energies of several MeV are often implanted into the optical materials to form waveguide structures of several microns beneath the surface of the sample. In this thesis, ion implantation has been used to form the waveguide and the performance of the waveguide has been studied in order to obtain the optimal fabrication conditions.Short-wavelength light sources have a wide range of applications in many areas. (For example: CD write on and read out, the seabed optical communications, laser medical, etc). As the technology of semiconductor laser with short-wave output is not yet mature, it is a viable assumption to use ordinary semiconductor laser (output wavelength of 0.82μm-0.84μm) with a combination of frequency doubling waveguide to get a short-wavelength laser source. Compared with the ordinary body-medium, waveguide can restrict the beam in a small range, even a moderate power laser beam can induce a high power density, which can lead to high frequency-doubling conversion efficiency. The conversion efficiency of frequency doubling is proportional to the power density of fundamental wave. Therefore, it is helpful to improve the conversion efficiency by using waveguide frequency doubling. Second, the phase-match of waveguide frequency doubling also has very prominent advantages.LiNbO₃ crystals are of great importance for fabrication of integrated devices due to their good intrinsic properties such as high electro-optic, acoustic-optic coefficient, excellent nonlinear optical properties, and high Curie temperature. As it has so many tremendous applications, the research of Lithium niobate has never been interrupted. At present, there are two major classical theories studying guided wave optics. One is the line optical theory, which is based on the linear optical transmission and the total reflection in the interface of the media, so that the light in the waveguide travels along the Z-shaped forward in the guide to analyze the various characteristics of the transmission within optical waveguide. Another theory is an electromagnetic theory based on Maxwell quations, which studies the various characteristics of waveguide by soluting the Maxwell equations meeting special conditions of the waveguide.In this paper, the second approach to study the characteristics of the waveguide frequency doubling is chosen, the principal tasks are summarized as follows:(1) we introduced the guided TE mode in the x-cut ion-implantated lithium niobate crystal waveguide, established a theoretical model from the Maxwell quations, gave a detailed process of calculating the Cherenkov radiation frequency doubling, got the conversion efficiency of the Cherenkov frequency doubling, and discussed the impact of a variety of factors, such as the injection depth, refractive index, the pump wavelength, etc., to the conversion efficiency of Cherenkov frequency doubling which provides the theoretical basis of optimization of the crystal ion implantation.(2) we studied the guided TM mode in the ion-implantaed z-cut lithium niobate crystal waveguide, gave a detailed process of calculating the Cherenkov radiation frequency doubling through the established theoretical model, and discussed the relations between the parameters, waveguide injection depth, refractive index, the pump wavelength, and the conversion efficiency of Cherenkov frequency doubling.