Phase-matched generation of coherent X-rays

Summary form only given. Recently, we have developed a new technique for generating coherent soft X-rays, that significantly improves upon both the average flux and the experimental practicality of these sources. The technique of high-harmonic generation uses the nonlinear-optical properties of an atom in the process of ionization to generate very high-energy (up to /spl sim/0.5 keV/sup 2/) coherent X-rays. In recent work, we showed that by propagating a high-intensity /spl sim/20 fs duration light pulse in a capillary waveguide, it is possible to match the phase velocity of the laser light and the X-rays over an extended interaction length in the wavelength range of 20-30 nm. This allows us to obtain very high (/spl sim/10/sup -5/) conversion efficiency of laser light to X-rays using modest /spl sim/0.2 mJ pulse energy, making it possible to implement HHG X-ray sources with microwatt average power using a small-scale, high repetition-rate laser. This technique can also be used to generate very intense and short-pulse ultraviolet and vacuum-ultraviolet radiation. The near diffraction-limited spatial coherence of these pulses, combined with their very short (possibly attosecond) duration, make this source attractive for a variety of new experimental investigations in X-ray science and nonlinear optics. In this talk, we will discuss our further development and optimization of this light source.