Theoretical Study Of Manakov Solitons In Two-Photon Photorefractive Materials

When the diffraction of optical beam is exactly balanced by the nonlinear effect in photorefractive medium, it's possible to form a photorefractive spatial soliton whose shape is unchanged. Comparing with other kinds of solitons, photorefractive spatial solitons can be realized with milliwatt level or even lower; in the photorefractive materials, meanwhile, waveguide is formed and stored, which can transmit beams without any energy lost. Photorefractive spatial solitons have a prospective application in many fields such as optical information processing, optical bistability, optical wave guiding and optical interconnection. Because of its feasibility on theory and experiment, research on photorefractive spatial solitons has attracted much interest recently.In this dissertation, Manakov solitons are theoretically studied both in biased two-photon photorefractive materials and in unbiased two-photon photovoltaic photorefractive materials, basing on the Castro-Camus two-photon photorefractive model.Basing on the theory of two-photon photorefractive spatial optical solitons and incoherently coupled spatial soliton pairs, the expression of spatial charge field is given concerning both biased and photovoltaic conditions in two-photon photorefractive materials, when the incidences are two incoherently coupled beams propagating co-linearly with the same polarization direction and the same wavelength.Beginning with the theory of two-photon photorefractive spatial solitons, the evolution of two incoherently coupled beams is studied in biased two-photon photorefractive medium, the existence of bright-bright, dark-dark, bright-dark Manakov solitons in the materials is confirmed theoretically. The relation between the configuration of soliton pairs and the direction of electrical field is discussed.The analytical solutions of bright-bright, dark-dark, bright-dark Manakov solitons under open-circuit conditions are deduced in two-photon photovoltaic photorefractive materials, as well as the relation between the type of soliton pairs and the direction of photovoltaic field is discussed.Finally, the transmission properties of Manakov solitons are analyzed in two-photon photorefractive materials, and the profiles of dimensionless intensity and the full width at half maximum of Manakov solitons are studied, as far as different parameters are concerned.