Engineered coherent soft-X-ray spectra for generating ultrashort soft-X-ray pulses

Using adaptive pulse shaping of the driving 800 nm laser pulse, we demonstrate for the first time the complete control over the XUV spectrum of high harmonics. We are able to generate arbitrarily shaped spectra of coherent soft X-ray radiation in a gas-filled hollow fiber. We achieve both the enhancement and suppression of high-harmonic emission in a selected wavelength region as well as the enhancement of coherent soft-X-ray radiation over a selectable extended range of harmonics. Adaptive control is performed by laser pulse shaper for the fundamental laser pulse based on a deformable mirror.