Demonstration of a Ni-Like Kr Optical-Field-Ionization Collisional Soft X-Ray Laser at 32.8 nm

We report the first experimental demonstration of a Ni-like optical-field ionization collisional soft x-ray laser. The amplifying medium is generated by focusing a circularly polarized 760 mJ, 30 fs, 10-Hz Ti:sapphire laser beam in a few mm cell filled with krypton. We have measured a gain coefficient of $78{\mathrm{c}\mathrm{m}}^{-1}$ on the $3d^{9}4d$ ${}^{1}S_0\mathrm{\text{−}}3d^{9}4p^1{P}_1$ transition at 32.8 nm, which is here amplified for the first time. This radiation source represents the shortest wavelength optical-field ionization collisional soft x-ray laser ever produced. The influence of the gas pressure and the pumping energy on the lasing output are also presented.

Figure 1

Schematic description of the experimental setup.

Figure 2

Time integrated spectrum of a 4-mm-long Kr plasma column irradiated by a 30 fs, 600 mJ laser pulses (20 shots).

Figure 3

Pressure dependence of the 32.8 nm $4d\mathrm{\text{−}}4p$ line of Ni-like Kr (solid dots) and the 41.8 nm $5d\mathrm{\text{−}}5p$ line of Pd-like Xe (open dots).

Figure 4

Driving energy dependence of the 32.8 nm $4d\mathrm{\text{−}}4p$ lasing line of Ni-like Kr (solid dots) and the 29.6 nm incoherent line (open dots).

Figure 5

Measured (squares) and calculated (line) intensities of the 32.8 lasing line as a function of the gas length.