The analytic expressions for steady-state electric field intensity and local density scale length in a plasma irradiated by a double-frequency laser are derived. It is shown that the ponderomotive force due to the double-frequency laser field leads to a local density dip near the critical surface and to the anomalous increase and fluctuation of the critical density scale length in some range of field intensity.

• Received 9 February 1988

DOI:https://doi.org/10.1103/PhysRevA.38.2996