Submicron focusing of high-energy X-rays with silicon saw-tooth refractive lenses: fabrication and aberrations

Saw-tooth refractive lenses are extremely well-suited to focus high energy X-rays (>50 keV). These lenses have properties of being continuously tunable (in energy or focal length), effectively parabolic, in-line, and attenuation-free on-axis. Vertical focusing of 60 keV synchrotron X-rays to 690 nm at a focal length f = 1.3 m with silicon saw-tooth lenses at a high-energy undulator radiation beamine is demonstrated, with discussion of relevant fabrication and mounting considerations and of geometrical aberrations unique to these devices. Aberration corrections towards further progress into the diffraction-limited nanofocusing regime are suggested. The versatility of such optics, combined with the attainability of smaller spot sizes at these penetrating photon energies, should continue to enhance material microstructure investigations at increasingly higher spatial resolutions.