Biased Two-photon Photorefractive Crystals Research Articles

Coherently coupled screening spatial soliton pairs due to the two-photon photorefractive effect

A theoretical study of coherently coupled spatial soliton pairs propagating along the same line in biased two-photon photorefractive crystals is presented. Our results show that coherently coupled bright–bright and dark–dark soliton pairs propagating collinearly can be supported in a steady-state regime under appropriate conditions. Moreover, the effects of the intensity ratio, the initial phase difference between two incident coherent beams, and various external bias fields on the existence conditions and properties of these soliton pairs have been discussed in detail. The stability of these soliton pairs has also been discussed by means of beam propagation methods. Finally, the temperature dependence of the dark irradiance and diffusion process on the intensity profiles and self-deflection of coherently coupled bright–bright soliton pairs are also analyzed.

Manakov solitons in photorefractive crystals with both the linear and quadratic electro-optic effects due to the two-photon photorefractive effect

We have first investigated Manakov solitons in biased two-photon photorefractive crystals in which refractive index changes are governed by both the linear and quadratic electro-optic effects simultaneously. Our results show that Manakov soliton pairs can be supported in all three possible realizations: dark-dark, bright–bright and dark-bright under steady-state conditions provided that the total intensity of the two mutually inherent beams is much lower than that of dark irradiance. It is also found that these Manakov solitons owe their existence to the co-effect of the linear and quadratic electro-optic effect where PR effect may be enhanced, weakened or even counteracted with each other. Moreover, the intensity full widths at half maximum of these Manakov solitons are inversely proportional to the square root of the quadratic polynomial of the external bias field, so the width can also be adjusted by altering the polarity besides changing the strength of the external biased field.

双光子光折变介质中基于两种电光效应的相干耦合孤子对

双光子光折变介质中基于两种电光效应的相干耦合孤子对

Incoherently coupled spatial soliton families in biased two-photon photorefractive crystals with both the linear and quadratic electro-optic effect

Different from the cases discussed preciously, nonlinear changes of refractive index in the photorefractive materials are influenced by both the linear and quadratic electro-optic effect simultaneously now. Here we present the evolution equations of one-dimension incoherently coupled spatial soliton families due to two-photon effect in biased photorefractive crystals with both the linear and quadratic electro-optic effect and discuss their existence conditions and properties in detail. Our analysis indicates that these soliton families can exist in all three possible realizations: dark-dark, bright-bright and dark-bright provided that the incident beams have the same polarization, wavelength and are mutually incoherent. Finally, the stabilities of these soliton families have been discussed by means of beam propagation methods.

Spatial solitons in biased two-photon photorefractive crystals with both the linear and quadratic electro-optic effect

Abstract The evolution equation of one-dimension spatial optical solitons resulting from two-photon effect in biased photorefractive crystals with both the linear and quadratic electro-optic effect is presented theoretically. Under appropriate conditions, our analysis indicates that bright, dark photorefractive spatial solitons can exist in the steady-state regime. The analytical solutions in the low amplitude regime are also obtained. Moreover, we theoretically discuss the self-deflection of bright solitons by taking the diffusion effect into account. Both the self-deflection effects follow a cubic polynomial of the applied bias field, and increase considerably at higher values of applied bias field. Relevant examples are provided.

Effects of temperature on the dynamic evolution of two-photon photorefractive screening spatial solitons

We investigate theoretically the temperature effects on the evolutions of both bright and dark screening spatial solitons in biased two-photon photorefractive crystals. For a stable bright or dark two-photon screening spatial soliton originally formed in a crystal at a given temperature, when the crystal temperature changes, it will evolve into another stable screening soliton if the temperature change is quite small, while it will become unstable or break down if the temperature change is large enough. The spatial shape of a stable two-photon screening spatial soliton can be changed by appropriately adjusting the crystal temperature.

双光子光折变晶体中两分量矢量空间孤子

To study the vector spatial solitons in biased two-photon photorefractive crystals, the dynamical evolution equation and the numerical solution of the vector spatial solitons are established. The bright-bright and dark-dark self-coupled vector solitons are predicted by using numerically methods. The dynamical evolutions of the bright-bright self-coupled vector spatial solitons are analyzed numerically. The results indicate that these self-coupled vector solitons can be obtained by using simple numerical integration procedures and their formation are irrespective to the ratio of the intensities of the two optical components. The bright-bright and dark-dark self-coupled vector spatial solitons exist steadily in two-photon photorefractive crystals.

Steady-state bright–dark vector spatial solitons in biased two-photon photorefractive crystals

We show that bright–dark vector solitons are possible in biased two-photon photorefractive crystals under steady-state conditions. The analytical solutions of these vector solitons can be obtained if the intensities of the two vector components are approximately equal. When the intensities of the two vector components differ, the vector soliton pair solutions can be determined using simple numerical integration procedures. The stability of the bright–dark vector solitons has been investigated numerically.