Computer simulations and experimental results on air-gap X-ray waveguides

High aspect ratio x-ray waveguide channels fabricated by e-beam lithography and wafer bonding

“…Hard x-ray nanobeams with cross sections in the range of d ' 10-100 nm enable novel nanoscale analytic techniques, adding nanoscale real space resolution to x-ray spectroscopy and diffraction, and enabling novel variants of coherent imaging and holography. A variety of optical elements can be used to generate x-ray nanobeams, such as Fresnel zone plates, [1][2][3][4] multilayer Laue lenses, 5 multilayer zone plates, 6 compound refractive lenses, [7][8][9] curved mirrors (e.g., in Kirkpatrick-Baez (KB) geometry 10,11 ), or x-ray waveguides, [12][13][14][15][16][17] as well as combinations of these elements. 6,18,19 The different optical elements impose significant challenges for nanostructuring and metrology, and progress in this field is often limited by the corresponding bottlenecks in fabrication.…”

“…6,18,19 The different optical elements impose significant challenges for nanostructuring and metrology, and progress in this field is often limited by the corresponding bottlenecks in fabrication. This is particularly the case for x-ray waveguides (WG), which deliver coherence filtered x-ray radiation with nanoscale dimensions in one spatial (1DWG) [12][13][14][15][16][17]20,21 or two spatial dimensions (2DWG). [22][23][24] Depending on the materials employed for the guiding and cladding layers, waveguides are capable to deliver beams of about 10 nm in cross section, 25 comparable to the record values achieved by other types of focusing optics.…”

“…X-ray propagation in waveguide channels has been studied both analytically [30][31][32] and by finite difference (FD) simulations, 17,[32][33][34] including generalizations to more complex structures and effects including both thickness variations and roughness, 35,36 which illustrate the challenges associated with fabrication.…”

Characterization of thin films for X-ray and neutron waveguiding by X-ray reflectivity and atomic force microscopy

“…Typically, electron beam evaporation is able to produce smoother films; although it has some limitations when a magnetic material has to be evaporated. This is the case in the present work, where we produce a WG with Ni cladding; potentially useful to produce polarized neutrons [13].…”

“…This characteristic has been used to produce micrometer and sub-micrometer X-ray [9,10] and neutron [11,12] beams with high gains in flux density (i.e. The beam is also highly coherent due to the interference of multiple reflected beams between top and bottom cladding [10,13]. The use of a thin-film WG as a polarizing device for neutrons has been, very recently, demonstrated [14].…”