Transition to the two-plasmon decay for increasing plasma density scalelengths

Two plasmon decay (TPD) instability is an important mechanism for laser energy deposition in underdense plasma even for ultrashort laser pulses provided that the laser intensities are high enough. The excitation of this instability depends also heavily on the plasma density scalelength. Important features associated with the TPD are the 3/2 harmonics emission and hot electron generation. Their angular distributions from numerical simulations are presented, showing the transition of the stimulated Raman scattering to the TPD when increasing the plasma density scalelengths.