Modulation instability of broad optical beams in biased two-photon centrosymmetric photorefractive crystals

In order to obtain the modulation instability of 1-D broad optical beams in biased two-photon centrosymmetric photorefractive crystals under steady-state conditions, the growth rate of 1-D modulation instability was obtained by means of numerical simulation method after treating the space-charge field locally. The numerical results show that the maximum modulation instability growth rates increases linearly with the external electric field and spatial-frequency when the incident optical intensity is constant. When the external electric field is fixed, the maximum modulation instability growth rates increases to a maximum then decreases as the incident optical intensity increases. The modulation instability of 1-D broad optical beams depends on the external bias field and the ratio of optical beam's intensity to that of the dark irradiance.