Two color soft x-ray laser
X and soft X-ray coherent sources are widely used tools to probe ultrafast dynamics of the matter on the nanometer scale. Among many of their features, the chemical selectivity provided by tuning the excitation wavelength to a core resonance is of paramount importance. The ability to operate them in a two-color configuration plays a key role in further development of pump-probe techniques. While different ways to provide two-color free-electron laser pulses are actively investigated, and a few characteristic experiments already carried out, we have developed a table-top two-color soft X-ray laser source using a laser-driven plasma of nickel-like ions.
We have shown that thanks to the high electron density in the plasma, besides the usual 32.8nm lasing transition in nickel-like krypton, stimulated emission can be triggered simultaneously on a neighboring radiative transition at 62.7nm, yielding a strong dual wavelength ASE signal. We found out that the gain dynamics of both transitions are comparable. The amplifier was seeded by a doubly resonant high-order harmonic pulse, producing a two-color short-duration and coherent laser beam. Both transitions offer similar prospects of pulse energy and duration and could lead to the delivery of intense and ultrashort two-color coherent soft X-ray pulses with a controllable delay.
