Focusing properties of hard x-ray photon sieves: three-parameter apodization window and waveguide effect

摘要

In this Letter, a three-parameter modified Kaiser apodization window is used to modulate the pinhole density on each ring of hard x-ray photon sieves, analyzing the guided-wave propagation inside the photon sieves' nanostructure. Theoretical analysis reveals that the waveguide effect can suppress the emergence of the high-order diffraction effect; the additional parameter of the modified Kaiser window function gives rise to new degrees of freedom for manipulating the FWHM and signal-to-noise ratio. Metal nanostructure thickness has no influence on the FWHM. Hard x-ray photon sieves with 90 deg phase shift (not 180 deg phase shift) can provide the best signal-to-noise ratio, which relaxes the nanofabrication constraints somewhat. Our work provides a robust way to design hard x-ray photon sieves.