One promising way to reach ultra-short soft X-ray lasers is to guide an intense infrared pulse through a plasma channel generated in a high pressure gas. However, in such a case, strong non-linear effects, as overionizationinduced refraction and self-focusing, hinder the propagation of the laser beam and thus the creation of the lasing ion and the population inversion. Using a particle-in-cell (PIC) code and a ray-tracing model, we demonstrate that a stable self-regulation mechanism between self-focusing and overionization appears, which enables guiding the infrared beam over several milimetres, well beyond the saturation length for amplification of the soft X-ray laser.
A PW Ti:Sapphire laser with 30-J energy and 30-fs pulse duration has been developed at GIST and applied to generate
x-rays and energetic charged particles. We present the status and plan of developing ultrashort x-ray sources and their
applications. We successfully demonstrated x-ray lasers and their applications to high-resolution imaging. In addition,
we plan to generate high flux x-ray/gamma-ray sources using the PW laser.