100 MW 1.6‐μm Pr+3:LaCl3 Propulsion Laser Pumped by a Nuclear‐Pumped He/Ar/Xe Laser

A 20 kHz, 100‐MW average power, pulsed 1.6‐μm Pr+3:LaCl3 up‐conversion laser for space propulsion, pumped at high intensity by a continuous 212‐MW, 2.026‐μm He/Ar/Xe nuclear‐pumped laser, is proposed. 1.6 μm falls within the 1.72 μm > λ > 1.53 μm atmospheric transmission window and is sufficiently distant from 1.4 μm to be relatively eye safe. The high pulse rate minimizes dribble and thus maximizes specific impulse. The nuclear‐pumped laser is also a steady‐state nuclear reactor. The Pr+3:LaCl3 solid‐state laser combines the many small beams produced by the reactor‐laser with high beam quality. It consists of an array of face‐pumped thin disks at Brewster’s angle, face‐cooled by high‐pressure turbulent helium. The inhomogeneities introduced by the disk array are corrected by using a double pass geometry with a phase‐conjugate mirror, as suggested by Magda. The fraction of the pump energy extracted from the Pr+3:LaCl3 laser is 47% at a pump intensity of 2×105 W/cm2. The He/Ar/Xe laser is 0.4% efficient, g...