X-ray flux enhancement in thin-film waveguides using resonant beam couplers

X-ray beam compression by tapered waveguides

“…1 These kinds of x-ray optics have first been realized as planar layered systems [one-dimensional waveguide (1DWG)], [2][3][4][5] and later also as two-dimensional confined channels (2DWGs), 6,7 as required for applications in coherent imaging. In contrast to most other nano-focusing optics such as Kirkpatrick-Baez (KB) mirrors, [8][9][10][11] Fresnel zone plates (FZP), 12 or compound diffractive lenses, 13 2DWGs deliver nanoscale x-ray beams with controllable spatial coherence.…”

Advanced x-ray multilayer waveguide optics

“…Several different ways have been used to generate x-ray modes, or more precisely to couple x-ray beams into WGs. Resonant beam coupling into planar waveguided with thinned cladding was used in early work [13][14][15][16][17]. Front coupling into planar waveguides with tunable air gaps was then demonstrated in [18], and later extended to two-dimensional waveguide channels [20,56,57].…”

“…Planar waveguide for hard x-rays are nowadays well established [13][14][15][16][17][18]. They can be simply realized by a thin film structure consisting of a low density (guiding) layer sandwiched in between layers of high density, the so-called cladding layer.…”

“…The basic aim of the experiment was to extend the principle of guiding electromagnetic radiation to the x-ray range. After further progress in synchrotron radiation, a few application experiments exploiting the RBC structure were published, including application of the guiding mechanism in a Si/Polyamin/SiO 2 structure [14], lensless projection phase contrast microscopy [15], forming x-ray standing wave [16], and providing attractive beam dimensions for microscopy [17]. Later a new ge-Introduction ometry of WGs, named front coupler (FC), had been introduced, both for onedimensional (1D) and two-dimensional (2D) waveguides.…”

“…For this application, the length of the waveguide L has to be sufficiently long to absorb all radiative modes in the cladding, re-quiring L to be in the range between 0.1 to 10 mm, depending on the photon energy. Generally, one distinguishes between one-dimensionally confining planar waveguided [13][14][15][16][17][18] and two-dimensionally confining channel waveguides (2DWG), which were introduced by [19], and which require advanced electron lithography with interferometric positioning and suitable pattern transfer techniques in order to reach the required aspect ratios. The fabrication of 2DWGs was improved by [20], and more recently extended from overgrown polymer channels to air channels capped by wafer bonding techniques [21,23].…”