High Average Power Table-Top Soft X-Ray Lasers Using Diode-Pumped Laser Drivers

Abstract

Soft X-ray lasers (SXRLs) produce the highest energy pulses of coherent ultrashort wavelength radiation. Their large number of photons per pulse allow us to perform single-shot imaging of nanoscale objects, to develop material composition sensitive nanoprobes, and to conduct interferometric diagnostics of bright dense plasmas. However, until recently, with the exception of capillary discharge lasers at 46.9 nm, their average power was limited by the low repetition rate of the high energy optical pump lasers required to drive them and by the relatively low pumping efficiency. To overcome this limitation, we have developed a diode-pumped, picosecond Yb:YAG CPA laser driver that allowed us to demonstrate the first table-top SXRL capable of 100 Hz repetition rate gain saturated operation. These new pump lasers combined with efficient plasma heating techniques enable the operation of SXRLs at four orders of magnitude higher repetition rate than the first plasma-based collisional SXRLs (Fig. 2.1). Laser operation at 100 Hz repetition rate generated an average power of 0.2 mW at 18.9 nm (Ni-like Mo) and 0.1 mW at λ = 13.9 nm (Ni-like Ag). We have recently improved upon this diode-pumped laser technology, demonstrating a record 0.5 kHz repetition rate, 1 J, picosecond laser with good beam quality and high stability. We will discuss the results of the first demonstration of a compact table-top soft X-ray laser at repetition rates up to 400 Hz using this new pump laser.