Research On The Nonlinear Modulation Of Photorefractive Surface Waves And Airy Beams

Photorefractive surface wave is a kind of nondiffracting beam that can be propagated at the surface of photorefractive materials due to the compensation between self-bending and total internal reflection.On the other hand,airy beam is a new kind of nondiffracting beam which can be accelerated in transverse direction.Among the most popular topics,surface waves in centrosymmetric or noncentrosymmetric photorefractive crystals,surface waves with two-photon photorefractive effect,spatial airy solitons in kerr nonlinear media and propagation and interaction of airy-guassian beams in saturable nonlinear media are investigated in detail in this paper.The primary achievements obtained are the following:For the localized surface waves at the interface between linear dielectric and biased centrosymmetric photorefractive(CP)crystals,if the propagation constant b is fixed,the energy of localized surface waves increases with the order of localized surface waves.For low b values,the considerable part of the energy of localized surface waves is concentrated in the linear dielectric and decreases with an increase in b.For high b values,the part of the energy of localized surface waves concentrated in the nonlinear CP crystals is always higher than that in the linear dielectric and increases with b.The stability properties of these localized surface waves are also discussed in detail.The propagation of nonlinear surface waves on the boundary of LiNbO3 crystal is investigated theoretically and experimentally.Surface waves with different oscillating period are obtained by varying the values of the propagation constant.The energy of surface waves increases monotonically with the propagation constant.The experimental results are in good agreement with theoretical analysis.The experimental results also show that the generation of surface waves can be shortened by increasing the power of the input beam and the excitation efficiency of surface waves can be enhanced by increasing the angle between the input beam and the crystal c axis.The paper presents a theory based on the Castro-Camus model that gives rise to the evolution equations of the optical beam at the interface between linear dielectric and two-photon photorefractive(TPPR)crystals.Three types of surface waves can be formed:delocalized surface waves,shock surface waves,and localized surface waves(LSWs).The results show that the transverse width and energy of LSWs increase with the increase in propagation constant if the order of LSWs is fixed,and for a given value of propagation constant.the transverse width of LSWs increases as the order of LSWs increases.LSWs can be stably in propagation along the interface of linear dielectric and the TPPR crystal.The propagation of airy beams in self-focusing Kerr nonlinear media:It is shown that spatial soliton with periodic oscillation can be formed out of the centered energy about the Airy main lobe during the propagation on the influence of higher initial energy.Full width at half maximum(FWIHM)of the soliton is reduced.The propagation trajectory of the shedding soliton can be controlled by adjusting the initial launch angle of airy beam.The propagation and interactions of Airy-Gaussian beams(AiGBs)in saturable nonlinear media:When a single AiGB with a certain power range propagates,it is shown that breathing soliton can be generated.Breathing periodic of the soliton become smaller first and then larger with an increase in initial amplitude.When two AiGBs in the in-phase case interact with each other,they attract each other and exhibit breathing soliton and symmetric soliton pairs near both sides of the beam center.In the out-phase case,they repel each other and exhibit only symmetric soliton pairs on both sides of the center.