  In this study we advocate the view that the cosmological constant is of
electromagnetic (em) origin, which can be generated from the collision of em
shock waves coupled with gravitational shock waves. The wave profiles that
participate in the collision have different amplitudes. It is shown that,
circular polarization with equal amplitude waves does not generate cosmological
constant. We also prove that the generation of the cosmological constant is
related to the linear polarization. The addition of cross polarization
generates no cosmological constant. Depending on the value of the wave
amplitudes, the generated cosmological constant can be positive or negative. We
show additionally that, the collision of nonlinear em waves in a particular
class of Born-Infeld theory also yields a cosmological constant.
