Published online by Cambridge University Press: 15 October 2013
In the present paper, spatial amplitude modulation instability arising due to relativistic self-phase modulation and relativistic cross phase modulation of two co-propagating, linearly polarized laser beams (with arbitrary relative polarization) interacting with homogeneous plasma, has been studied. Wave equations including finite perturbation length effects, group velocity dispersion, and coupled nonlinear source term have been set up. Coupled dispersion relation for the two laser beams has been derived and solved numerically. The growth rate of modulation instability has been obtained and compared with the growth rate of a single beam propagating in homogeneous plasma. It has been shown that modulation instability of a single beam may either be enhanced or suppressed by co-propagation of another laser beam having appropriate polarization.