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In this research, design and fabrication of an integrated heterodyne electrooptic modulator in lithium niobate have been presented. In this modulator, the waveguide is made by using proton exchange process; to exert two high frequency signals, deposited electrodes with Mach-Zender arms between them are used. In this method, every electrical signal is applied on one of the Mach-Zender arms, so that it can be stimulated by one specific frequency; these two signals are united optically to create frequencies equal to sum and subtraction of the input signal frequencies in the output. Also, by using finite element method, the influence of proton diffusion scale in the output light mode, electrode dimension, and configuration in the overlap integral of the light mode and electrical field, as well as electrode impedance, is estimated.

The acoustic wave velocity depends on elasticity and density at most materials, but because of anisotropy and especially piezoelectric coupling effect, the acoustic wave propagation at piezoelectric based crystalloacoustic materials, is an applied and challenging problem. In this paper, using modified Christoffel's equation based on group velocity concept, the effect of anisotropy and piezoelectric coupling at different wafers of lithium niobate crystalloacoustic (strong anisotropy) on acoustic wave velocity (semi-longitudinal, semi-vertical transverse wave and semi-horizontal transverse wave) is investigated, and validated by experimental data. Then, the acoustic wave velocity ranges that can be supported are determined. The result of this study can be essential at acoustic metamaterials design, Phononic crystal and piezoelectric based wave-guides.

In this research, the capability of new approach of making ridge waveguides in lithium niobate by Argon physical etching and diffusion of titanium is investigated. For this purpose, the proportion of light mode confinement in the ridge section is measured and compared to simulation results. Also the effect of ridge wall defects -which is a challenge of this kind of waveguides- in light power dissipation, is simulated. The ridge height reaches 2.5µm and the defects of ridge walls are measured to be about 200nm on average. In this research, by simulation of titanium diffusion and refractive index change of the waveguide it is demonstrated that although the defects exist in the ridge walls, by using appropriate diffusion depth of titanium and refractive index distribution, light power dissipation less than 3 dB/cm can be reached while mode confinement in the ridge section is more than 50 percent.