Generation of Efficient Optical-Field-Ionization X-Ray Lasers in Cluster Jets

Abstract

We experimentally demonstrate the amplification of optical-fieldionization soft x-ray lasers in krypton cluster jets at pump energy of only 200 mJ. With the employment of small f-number optics, nature diffraction and ionizationinduced refraction in plasmas can be suppressed to enable the pump pulse producing a longer column of gains provided the focal position is optimized. A simple wave propagation code is developed to study and optimize the laser propagation in optical-field driven plasmas. Good agreements between experimental observations and simulations are found. The further enhancement of Kr x-ray laser output at 32.8 nm is achieved by guiding the pump beam in the optically preformed plasma waveguide. More than 4 times of x-ray photons are generated from pure Kr plasma waveguide at the same pump energy. Significant reductions of the pump energy make these pumping configurations favorable for practical high-repetitionrate operations.