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

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