High Power Ultrashort Pulse Lasers to Pump Plasma-Based Soft X-ray Lasers

High energy ultrashort pulseoptical lasers operating at high repetition rate are required to drive intense compact coherent soft x-raysources, including soft x-raylasers (SXRLs), for applications in nanoscience, material studies, and high field science. This paper reviews two types of high power solid state lasersystems to pump compact, high repetition rate, plasma-based SXRLs. One is a flashlamp-pumped, petawatt-class Ti:sapphire chirped-pulse amplificationlaser that generates 0.85PW pulses of 30fs duration at 3.3Hz repetition rate. Using this laser, we have demonstrated gain-saturated, compact, repetitive lasers down to 6.85nm in Ni-like Gd and observed gain down to 5.85nm in Ni-like Dy. The second type of pump laser is an all diode-pumped CPA system based on cryogenically cooled Yb:YAG active mirror amplifiers that produces 1J pulses of picosecond duration at 500Hz repetition rate. These compact laser systems have enabled new advances in high-average-power tabletop SXRLs that include 100 Hz demonstrations at wavelengths ranging from 10.9nm to 18.9nm, as well long duration operation at these high repetition rates for periods up to one hour. These and other recent results including the operation of an 18.9nm Ni-like Mo laser at 400Hz repetition rate open a path to compact kilohertz repetition rate SXRLs.