Observation of amplification of light by Langmuir waves and its saturation on the electron kinetic timescale

摘要

Experiments demonstrate the ～77× - amplification of 0.5 to 3.5-ps pulses of seed light by interaction with Langmuir waves in a low density (1.2 × - 10~(19) cm~(-3)) plasma produced by a 1-ns, 230-J, 1054-nm pump beam with 1.2 × - 10~(14) W/cm~2 intensity. The waves are strongly damped (kλD = 0.38, Te = 244 eV) and grow over a ～ 1 mm length, similar to what is experienced by scattered light when it interacts with crossing beams as it exits an ignition target. The amplification reduces when the seed intensity increases above ～1 × - 10~(11) W/cm~2, indicating that saturation of the plasma waves on the electron kinetic time scale (<0.5 ps) limits the scatter to ～1% of the available pump energy. The observations are in agreement with 2D PIC simulations in this case.