KEYWORDS: Luminescence, High angular resolution imaging, Anisotropy, Photonics systems, Gallium nitride, Electron beams, Scanning electron microscopy, Metamaterials, Electron microscopes
The photonic band structure of plasmonic and nanophotonic materials and devices can be controlled by physical features much smaller than the optical diffraction limit. We present a methodology to correlate nanoscale structure to the photonic band structure directly using the cathodoluminescence (CL) signal generated by a sample in the scanning electron microscope. Further to conventional electron microscope imaging, we record the wavelength- and angular- distributions of luminescence in a highly-parallelized manner. The result is a wavelength- and angle- resolved data cube, which was transformed to observe the emission intensity in the energy-momentum basis revealing the photonic band structure.
We demonstrate a compact instrument for rapid and accurate measurements of the absolute and local efficiency of soft x-ray
zone plates in the water window [M. Bertilson, et al, Rev. Sci. Instrum 78, 026103 (2007)]. The arrangement is based
on a new single-line λ = 2.88 nm liquid-nitrogen-jet laser-plasma source. The versatility of the instrument enables micro
and condenser zone plates with focal lengths in the range from ~200 μm to ~100 mm to be measured. We demonstrate an
accurate local efficiency map of a in-house fabricated micro zone plate. Furthermore, we show how this compact
instrument allows rapid feedback to the fabrication process which is important for future improvements.
We present the theory and implementation of a numerical model capable of simulating two-dimensional images for an x-ray
microscope using partially coherent illumination considerations. Partially coherent illumination is found in all x-ray
microscopes and particularly in the latest generation of our in-house compact soft x-ray microscope. This is due to an
introduced mismatch in numerical aperture of the condenser and objective zone plate, and will yield diffraction-like
artifacts in phase-shifting objects. The numerical model approximates the condenser zone plate as a secondary incoherent
source represented by individually coherent but mutually incoherent source emitters, each giving rise to a separate
image. A final image is obtained by adding up the image intensities of the individual contributions. The simulation has
been a useful tool for investigating the influence of coherence on images in both the mirror and zone plate condenser
arrangement of the in-house compact soft x-ray microscope. The latest development included in the program is the effect
of astigmatism and partial coherence, where the calculated results show good qualitative agreement with respect to the
microscope images.
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