Acousto-optic Devices Based On Periodically Poled LiNbO3

We study acousto-optic (AO) devices based on periodically poled lithium niobate(PPLN). Acousto-optical devices include surface acoustic wave devices and acousto-optic tunable nonliner effects devices. Nonlinear effects include acousto-optic (AO) tunable second harmonic generation (SHG) and the fundamental wave. In this thesis, we propose a suitable super-lattice structure of lithium niobate, based on the unique piezoelectric effect and AO effect, we design a series of functional optical devices. It plays a positive role in practical field of lithium niobate super-lattice. The major work in this thesis includes.1. Surface acoustic wave is generated by acoustic super-lattice. By using Green's function theory and computation we analysis the different structure of the response, and we also conduct comparative analysis. First we theoretically certificate difference that the different proportion of positive and negative domain has an affect on the acoustic super-lattice. Second we extend to the generation of surface acoustic wave, in order to verify the role of finger width ratio. And the acoustic super-lattice can produce high-frequency acoustic waves, it can be used to replace the conventional surface acoustic wave devices and be more easily available. 2. AO tunable SHG is proposed in PPLN. The acoustic wave could either be induced from an external transducer or self-generated in PPLN driving with a cross-field radio frequency field. The reciprocal vector of PPLN compensates the SHG wave-vector mismatch when QPM condition is satisfied, while phonons with suitable frequencies may affect it by scattering photons to different polarization state. The QPM SHG and AO polarization rotation are coupled together. Second harmonic waves' intensities, polarization states and even phases thus could be manipulated instantly through AO interaction.3. We propose that acousto-optic tunable fundamental wave in second harmonic generation process based on periodically poled lithium niobate(PPLN). Through the external acoustic transducer, we make the fundamental wave deflection, then some new physical phenomena happen. The Z-polarized fundamental wave generate Y-polarized fundamental and Z-polarized second harmonic. The Y-polarized fundamental wave also generate Z-polarized fundamental and second harmonic wave. Both Y and Z polarized fundamental waves can generate second harmonic that shows the results of periodic change, if the phase between Y and Z direction fundamental is different. When it makes very small phase change, the result of SHG makes a great change. So the phase has relatively great influence the structure, which may be used in some sensing or measurement devices.