Possibility of near diffraction-limit size X-ray beam by higher order harmonic generation

Laser generation in the X-ray region has become realistic because of the construction of free electron laser facilities, which will be available in the near future (Linac Coherent Light Source (LCLS) at Stanford in 2009; European XFEL in 2014). Another significant route is the extension of existing laser technologies such as high-order harmonic generation (HOHG), particularly from relativistically oscillating plasma mirror-like surfaces. Professor M. Zepf (Queens University Belfast, UK) and his colleagues recently published an interesting paper showing that it is possible to achieve a near-diffraction-limited focal spot size that is also controllable. For more information, see the paper, "Diffraction-limited performance and focusing of high harmonics from relativistic plasmas", B. Drome et al., Nature Physics, advanced online publication doi:10.1038/nphys1158