Parametric decay of laser into two electromagnetic waves in a rippled density plasma

Abstract

The presence of a density ripple in an unmagnetized plasma is shown to allow parametric decay of an electromagnetic wave into two electromagnetic waves, which is otherwise not allowed due to wave number mismatch between the decay waves. The static density ripple accounts for the mismatch. The decay occurs at plasma densities below the quarter critical density and the decay electromagnetic waves propagate at angles to the pump laser. The requisite ripple wave number q increases with the increase in pump wave frequency. However, as the ripple orientation with respect to the pump θR increases, q decreases. The growth rate for the parametric instability initially decreases with the frequency of the lower frequency electromagnetic wave, attains a minimum and then increases. The growth rate is higher for lower values of θR.

Nonlocal theory of electromagnetic wave decay into two electromagnetic waves in a rippled density plasma channel

“…A rippled density plasma, however, offers the possibility of such a decay when the uncompensated momentum between the interacting waves can be shared by the ripple. Sati and Tripathi 11 have demonstrated such a possibility in unbounded plasma. The interaction demands that the three electromagnetic waves be noncollinear.…”