Seeded Soft X-Ray Lasers: Towards OAM Beam Amplification and Quasi-Pi-pulse Regime

We present in this paper ongoing studies on seeded plasma-based soft X-ray lasers using the LASERIX facility. After an overview of the source setup and characteristics, we will discuss two prospects that might increase the interest of these coherent soft X-ray sources. We have successfully generated harmonic beams carrying Orbital Angular momentum. We briefly present this experiment and discuss the remaining challenges for amplifying these kinds of beams in a plasma-based soft X-ray laser. In the second part, we present numerical results on harmonic seed amplification in conditions leading to Rabi oscillations. This regime is known to be a promising way to reach femtosecond pulses in the present plasma amplifiers. We will discuss the possibility of increasing the stability of such a regime by the introduction of a continuous refractive loss in the gain region.