Group Velocity Modulation Based On Electro-optic Effect In Periodic Poling Of Ferroelectric Crystal

Laser has been hailed as one of the most significant inventions in20th century in physics. The study of laser has attracted much attention of several generations of scientists for decades, since from the laser was found, creating, understanding, and using.The birth of laser made the world reinterpretate the concept of light, and made us have the knowledge that optics phenonmena can be further extended from I i nearity to nonlinearity. Most of the optical phenomena in our life are nonlinear optical phenomena So the emergence of laser provides more possibilities for human’s life.The electro-optic effect is a significant effect of second-order nonlinearity in ferroelectric crystals. According to different applied directions of applying electric field, it can be divided into two categeroies, one is longitudinal electro-optic effect and another is transverse electro-optic effect. The principal theory of this thesis is based on nonlinear optical electro-opti c effect, and the content of the thesis is focused on the group velocity modulation of slow lightin periodically poling lithium niobate crystal.Firstly.we introduce the development of optics roughly, and explain the concept of phase matching. Secondly, the structural model of ferroelectric crystals and two kinds of electro-optic effect are shown in detail. At last, we drive the second-order nonlinear coupled wave equations in the presence of DC electric field, and take the nonlinear shift induced by third-order nonli nearity effect into account to the modulation of group velocity of ultra-short pulse. Moreover, we analyzes emphatically the roles and effects of impact factors such as electric field strength, temperature, intensity of input pulse, and the length of period on the modulation of slow light in both the interacition effects of second-order and third-order nonlinearity and the second-order nonlinear effects acting alone. The results show that the modulation effect resulting from the interaction between second-order and third-order nonlinearity is greater than the effect of second-order nonlinearity acting alone under theidenticai condition of input parameters.