Pulsed Mid-infrared Radiation from Spectral Broadening in Laser Wakefield Simulations*

Spectral red-shifting of high power laser pulses propagating through underdense plasma can be a source of ultrashort mid-infrared (MIR) radiation. During propagation, a high power laser pulse drives large amplitude plasma waves, depleting the pulse energy. At the same time, the large amplitude plasma wave provides a dynamic dielectric response that leads to spectral shifting. The loss of laser pulse energy and the approximate conservation of laser pulse action imply that spectral red-shifts accompany the depletion. We investigate, through simulation, the parametric dependence of MIR generation on pulse energy, initial pulse duration, and plasma density.