Efficient Doppler-Effect-Induced Generation of Mid-IR Radiation upon Reflection of Intense Laser Pulses from a Near-Critical Density Plasma

We consider a possibility of generating mid-IR radiation due to the Doppler effect upon reflection of relativistically intense radiation produced by the planned XCELS laser facility from a near-critical density plasma. It is shown that the highest efficiency on the order of tenths of a percent is observed at the shortest possible duration of the incident laser pulse and its ultratight focusing into a spot with a diameter of less than 2 μm. The use of two pulses allows the efficiency to be increased by 1.5–2 times. Thus, it is possible to generate radiation pulses in the region above 3 μm with an energy of several joules.