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Focused X-Ray Vortices

We designed and fabricated amplitude DOEs to generate X-ray vortices with high TC and tested them in scanning and full field microscope setup configurations. DOE function is calculated summing a helical wave with a desired TC to a spherical wave. In the scanning setup we used a the DOE as microscope objective and demonstrated the doughnut intensity pattern characteristic to the vortex but we could not characterize the phase distribution.

In the full field X-ray experiment [1] we used larger DOEs that generate a high focused TC vortex (l=32). The vortex DOE, fabricated at TASC-LILIT beamline, has the following characteristics: 220 nm gold on 100 nm silicon nitrade membrane, 300 nm resolution, 614 um diameter, 111 mm focal length at 720 eV. The DOE, placed in the condenser position converts the X-ray input beam into a helical beam focused in the sample plane where the intensity pattern is a doughnut with radius proportional to the square root of the topological charge.
In order to characterize also the phase distribution characteristic to the vortex field we used the interference between the zero order beam and the vortex.

The obtained interference pattern demonstrates the phase distribution characteristic to the optical vortex with the topological charge l=32. Possible applications of the interaction of these beams with the matter [2] are also discussed.

References

[1] Di Fabrizio E., Cojoc D., Cabrini S., Kaulich B., Susini J., Facci P., Wilhein T., Optics Express, 11, 2278-2288, (2003)
[2] A. Alexandrescu, D. Cojoc, and E. Di Fabrizio, Phys.Rev. Lett. 96, 243001 (2006).

Last Updated on Wednesday, 28 September 2011 15:15