Shanghai Optical Machinery Institute has made progress for the first time in hard X-ray zoom beam imaging

Recently, the High Power Laser Physics Joint Laboratory of Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, completed the research of hard X-ray zoom beam splitting imaging on the micro focus X-ray source for the first time, and solved the problem of beam splitter limitation in the hard X-ray band. The related achievements are titled "Bifocal photo scene imaging in the hard X-ray region" and published in Optics Letters.

The Fresnel zone plate was proposed in 1818 and successfully applied in X-ray focusing research in the 1960s. The emergence of photonic screens in 2001 provided a device choice for high-performance focusing of X-rays beyond zone plates. However, traditional zone plates and photon sieves have single focal characteristics and cannot meet the beam splitting requirements of shortwave diffraction imaging and interferometric sensing. With the solution of the problem of high coherence shortwave light sources, the demand for X-ray beam splitters has become more urgent.

Researchers used the ancient Greek ladder sequence to encode traditional photon sieves and optimized the design of a hard X-ray bifocal photon sieve. With the help of Professor Chen Yifang's research group at Fudan University, the device was processed and tested, as shown in Figure 1. By using copper foil to filter the microfocal X-ray source, a spectral line with a half width of 0.0242 keV and a center of 8.39 keV was obtained, with the X-ray source mainly concentrated at 7.38 keV, 8.39 keV, 9.67 keV, 9.96 keV, and 11.29 keV. On this basis, equal size imaging experiments were conducted on the dual focus photon sieve, which were recorded by X-ray CCD, as shown in Figures 2 and 3. The experimental results show that regardless of whether it is long focus or short focus imaging, the images recorded by the detector during the forward and backward movement process first decrease and then increase, fully proving that the dual focus photon screen achieves zoom beam splitting imaging. The emergence of hard X-ray beam splitters has expanded new development space for applications such as variable resolution diagnosis of laser plasma, X-ray microscopy, and beam splitting coherent diffraction imaging.

The relevant work has been supported by the National Natural Science Foundation of China, the Chinese Academy of Sciences strategic leading science and technology special category A and other projects.

Figure 1: Double focal photon sieve, (a) under optical microscope, (b) under scanning electron microscope, (c) under minimum hole, (d) under gold height

Figure 2 Experimental results of telephoto imaging, where (a-i) the detector gradually approaches the image plane and then moves away from it

Figure 3 Experimental results of short focus imaging, (a-c) detector gradually approaches the image plane and then moves away from the image plane

Source: Shanghai Institute of Optics and Mechanics