| Spatial optical solitons can be generated under low incident light intensity through the phenomenon of optical self-phase modulation.They possess enormous potential applications.However,during the process of transmission in a medium,solitons are affected by modulation instability,which is also referred to as a precursor to soliton formation.Due to their excellent characteristics and relatively easy generation conditions in nonlinear crystals exhibiting both linear and quadratic electro-optic effects,spatial optical solitons have become one of the hot research topics in soliton studies.Modulation instability is a precursor to soliton formation,and therefore,in depth analysis and investigation of modulation instability is an indispensable aspect in the field of solitons.This article presents a systematic theoretical study of one-dimensional modulation instability of broad light beams in optically-induced linear and quadratic electro-optic media.Firstly,starting from the band transport model describing the single-photon optical beam deflection effect,the optical field equation in the electro-optic medium under the coexistence of linear and quadratic electro-optic effects is derived under the action of an external electric field.Bright and dark soliton solutions in the form of integrals are obtained,and the conditions,properties,and transmission laws of the solitons are verified.Secondly,the theoretical analysis of one-dimensional modulation instability of broad light beams in optically-induced linear and quadratic electro-optic crystals under the coexistence of linear and quadratic electro-optic effects is presented.The global and local modulation instability growth rates and peak values are derived,and the influence of the external electric field intensity and polarity and the ratio of light intensity to dark irradiance during the modulation process is determined.Finally,the temperature effect of the one-dimensional modulation instability of broad light beams in photorefractive crystals with coexistence of linear and quadratic electro-optic effects is analyzed,including the forms and influences of the relative dielectric constant,dark irradiance,and diffusion effect,and the temperature dependence of the dark irradiance during the modulation process is determined. |
