Phase shifting is a key technique in in-line digital holography. It prevents the reconstructed image from vague caused by its twin image and the direct current term. However, traditional phase shifters have their own restrictions especially in short wavelength regions such as X-rays and EUV. Recently, researchers at Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, have introduced a kind of phase-shifting diffraction lens named Greek-ladder sieves into in-line digital holography. They firstly introduced the phase-shifting principle of Greek-ladder sieves. Greek-ladder sieves are designed based on Fresnel zone plate by replacing the bright rings with isolated pinholes, whose locations relate to Greek ladders and sizes are specially designed. Greek-ladder sieves generate three dimensional arrays of diffraction-limited foci with equal intensity but different phase values, thus making phase shift possible. In the following experiment, they designed two kinds of phase-shifting sieves and separately used them to image a 1951 U.S. Air Force resolution test target and three-dimensional array(11*11) *2 foci. The experimental results agree well with the theoretical analysis and verify the validity of the phase shift function of amplitude-only Greek-ladder sieves. In developing the next generation of synchrotron light sources (free-electron lasers), this kind of phase-shifting sieve with amplitude-only modulation will offer an opportunity for X-ray holography, biochemical microscopy at short wavelengths, and X-ray spectroscopy in physical and life sciences.
This research, entitled "In-line digital holography with phase-shifting Greek-ladder sieves" has been published on April 9, 2018 at the Appl. Phys. Lett. This work was supported by the National Natural Science Foundation of China and Youth Innovation Promotion Association CAS. Article Website: https://aip.scitation.org/doi/10.1063/1.5022816
FIG. Optical conguration of in-line holography with phase-shifting Greek-ladder sieves.（Image by Jing Xie）
Mr. Cao Yong General Administrative Office Shanghai Institute of Optics and Fine Mechanics, CAS Email: email@example.com