Transverse Localization Of Weakly Modulated Photonical Lattices Based On Two-photon Photonrefractive Effect

Discrete diffraction is a familiar optical phenomenon in periodic structureswhich first proposed and observed in waveguide system. It’s easily use optical inducetechnique to form periodic photonic lattices that is similar to waveguide system inphotorefractive crystals. Optical beam propagation in the periodic lattice system isexpected to experience typical diffraction properties and it will appear transverselocalization in horizontal scales when nonlinear involved. With these splendidperformance, the research on this domain have attractive application perspective inall-optical switching and routing, optical connection, optical information processing,optical integration.Two-photon photorefractive materials can construct space-charge field throughtwo-photon effect which contains the process of secondary excitation ofphoto-generated carriers. According to the experimental results, we can draw theconclusion that lattices formed by this mechanism is more stable than that created bysingle-photon effect. So using two-photon materials to explore discrete diffractionand transverse localization is more likely to reach the prospective objective andprovide convenience condition for experiment.At first, the research findings on the development progress from discretediffraction to discrete solitons are introduced and analyzed in this paper. From thetheory model of two-photon effect, the refractive index expression is obtained andwe also derive a form of propagation dynamic evolution equation based onMaxwell’s laws. Finally we provide how to use beam propagation method andpresent specific procedure in Matlab circumstance.Weakly modulated photonic lattice has some advantages compared withwaveguide arrays. We can adjust and manipulate the period of photonic lattice timelyby changing the incident angle of two optic beam. what’s more, the nonlinear symboland strength is determined by voltage applied on crystals. In this paper, we stress ontwo different style photonic lattices based on two-photon effect and there are manyprofound discussion, analysis and simulation for them in the following. In thesimulation, We first explore the propagation characteristic of probe beam incontinuous system and show the diffraction pattern in different voltage polarity anddifferent electric magnitude values. In discrete system, square and hexagonalbackbone structure are studied mainly, there are many factors influencing the graphof diffraction, including voltage applied on two-photon materials, refractive indexvalue, voltage polarity, on-site or off-site excitation, linear or nonlinear condition etc..Around those factors refered to above, we analyze and discuss the simulation resultsin detail.