Research Of Waveguide And Grating Based On LiNbO₃

In recent years, the optical communication technology develops rapidly, building all-optical communication network integrated optical devices becomes a hot topic, and waveguide device is an important part of many integrated optical devices, waveguide grating has lots of functions, including coupling structure, beam, reflection, filter, focus, diffraction and etc.. Li Nb O3 rolled optical properties, non-linear, photorefractive effect into one, which has lots of advantages like high stability, easy to grow and polished, low cost, the wavelength range from 0.4 to 5mm has good light transmission performance, Li Nb O3 is a very high quality electro-optic material which has been widely used in the production of electro-optic modulator, wavelength converters and etc. the most widely used Li Nb O3 waveguide technology is Ti diffusion and proton exchange(Proton Exchange: PE), the production process of the waveguide gratings are now more commonly used electron beam lithography, focused ion beam etching, and femtosecond laser photorefractive Reform carved etc.In this thesis, we analysis the waveguide which was fabricated on X-cut Li Nb O3, also did some early experiment of carved grating on its surface. Details are as follows:First, the theoretical analysis is given by a single-mode transmission conditions and the effective refractive index of the waveguide effect of different size on the size of the loss to be analyzed, concluded: waveguide loss increases with the size reduction; waveguide is fabricated on X-cut Li Nb O3 by Ti diffusion, whose length is 13.5mm, width is 8 mm, the effective refractive index, waveguide thickness, loss is measured. There has a higher temperature difference between samples and photoresist during the process of spinning coating, which can impact the loss of the waveguide. Experiment results show that the sample fabricated by lower temperature difference has lower transmission loss.Second, Bragg grating is etched on the Ti-diffusion LN waveguide which support TE mode and TM mode, so a double wavelength filter can be achieved. Analysis the influence of the duty cycle of the grating etched, etch angle and etch depth on the waveguide, the results show that the grating with 1/2 etching duty cycle and less than 15°etching angle has the best maximum reflective. The reflectivity and bandwidth increase with the increase of etching depthThird, a equipment and method using a femtosecond laser inscribing the grating is proposed, which is simple and flexible, can carves different types of gratings, and the method which etched different types is described in detail, using the equipment, we dot on Li Nb O3, optical power and exposure time were compared, getting good parameters by collecting and analyzing the data.