Shanghai Institute Of Optics And Precision Machinery Makes First Progress in Hard X-ray Zoom Beam Splitting Imaging

Recently, the Joint Laboratory of High Power Laser Physics of Shanghai Institute of Optics and Precision Machinery (SIPM), Chinese Academy of Sciences (CAS), has accomplished the first study of zoom beam imaging of hard x-rays on microfocused x-ray sources, and solved the problem of beam splitter limitation in the hard x-ray band. The results were published in Optics Letters under the title of "Bifocal photon sieve imaging in the hard x-ray region".
The Fresnel ribbon sheet was proposed in 1818 and successfully applied to x-ray focusing in the 1960s, and the emergence of the photon sieve in 2001 provided an alternative to the ribbon sheet for high-performance focusing of x-rays. However, the conventional waveplates and photon sieves are monofocal in nature and cannot meet the beam splitting requirements of short-wave diffraction imaging and interference sensing. With the solution of the problem of high-coherence short-wave light source, the demand for x-ray beam-splitting devices becomes more urgent.
The researchers optimized the design of a hard x-ray bifocal photon sieve by encoding the traditional photon sieve with the help of the ancient Greek ladder sequence, and completed the processing and testing of the device with the help of the group of Prof. Yifang Chen of Fudan University, as shown in Fig. 1. By using copper foil to filter the micro-focus x-ray source, the spectral lines with a half-value full width of 0.0242 keV center 8.39 keV were obtained, in which the x-ray source is mainly concentrated in 7.38 keV, 8.39 keV, 9.67 keV, 9.96 keV, 11.29 keV. Based on this, the bifocal photon sieve was subjected to iso-large imaging experiments, which were recorded by the x-ray CCD, as shown in Fig. 2 and Fig. 2, respectively. recordings were performed, as shown in Figs. 2 and 3. The experimental results show that, regardless of the long-focus or short-focus imaging, the detector in the back and forth movement process recorded image is first smaller and then larger, fully proved that the bifocal photon sieve to achieve the zoom beam splitting imaging. The emergence of the hard x-ray beam splitter expands new development space for applications such as variable-resolution diagnosis of laser plasma, x-ray microscopy and split-beam coherent diffraction imaging.
This work is supported by the National Natural Science Foundation of China and the Class A Strategic Pilot Program of the Chinese Academy of Sciences.

Figure 1 Bifocal photon sieve, (a) optical microscope photo, (b) scanning electron microscope photo, (c) smallest hole, (d) gold height

Fig. 2 Experimental results of telephoto imaging, (a-i) the detector gradually moves closer to the image plane and then away from it

Fig. 3 Experimental results of short-focus imaging, (a-c) detectors gradually approaching the image plane and then moving away from the image plane