X-ray beam compression by tapered waveguides

Abstract

We have fabricated linear tapered waveguide channels filled with air and imbedded in silicon for the hard x-ray regime, using a processing scheme involving e-beam lithography, reactive ion etching, and wafer bonding. Beam compression in such channels is demonstrated by coupling a pre-focused undulator beam into the channels, and recording the exit flux and far-field diffraction patterns. We achieved a compressed beam with a spot size of 16.48 nm (horizontal) × 14.6 nm (vertical) near the waveguide exit plane, as determined from the reconstructed near-field distribution, at an exit flux which is eight times higher than that of an equivalent straight channel. Simulations indicate that this gain could reach three to four orders of magnitude for longer channels with tapering in two directions.

Surface and interface characterization of Ru/C/Ru trilayer structure using grazing incidence X‐ray reflectivity and X‐ray fluorescence

“…33 Chen et al have observed that the transmission of tapered waveguides reduces to 0.96% from expected 8.9% due to the interfacial roughness and internal defects. 34 Prudnikov has shown that the field intensity inside the multilayer-based waveguide reduces by about 16% to 20% when rms roughness of all the layers is increased from 0 to 0.5 nm. 35 Thus, the lower densities of Ru layers and interfacial roughness of the sample deteriorate the field intensity inside the guiding layer.…”

A matter of brightness: table-top X-ray generation inside waveguides and X-ray holography with single free-electron laser pulses

“…Once the technical challenges for channel waveguides are solved, X-ray generation in waveguides beyond straight channels like tapered channels [CHS15], beamsplitters [HS16], split-and-delay lines or bent channels [Sal+15a] can provide entirely new possibilities for source designs. This toolbox of optics on a chip can be especially interesting for quantum optical experiments with hard X-rays at table-top instruments.…”