Shanghai Institute of Optics and Fine Mechanics has achieved beam splitting vortex control and interference detection for the first time in the 46.9nm wavelength band

Recently, Associate Researcher Zhang Junyong from the High Power Laser Physics Joint Laboratory of the Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, together with Professor Zhao Yongpeng's research group from Harbin Institute of Technology and Professor Zhan Qiwen's research group from Shanghai University of Technology, completed the experimental verification of 46.9nm band splitting vortex control and interference detection for the first time, opening up a feasible technical path for shorter wavelength structural splitting control and soft X-ray array structural imaging. The related achievements were published in Nanophotonics under the title "Vortex bifocusing of extreme ultraviolet using modified Fermat spectral photon sieve splitter".

Fresnel zone plates were successfully applied to X-ray focusing in the 1960s, and the emergence of photon screens in 2001 provided a device choice different from traditional zone plates for high-performance focusing of short waves. Vortex light carries orbital angular momentum, and its spiral phase wavefront causes a phase singularity at the center, resulting in a hollow beam. This has important potential applications in particle manipulation, optical communication, quantum information processing, high-resolution microscopy imaging, and other fields.

In principle, various types of spiral lines can generate similar vortex light fields. Based on this guiding principle, researchers have designed an improved Fermat spiral photon sieve for vortex beam splitting at a wavelength of 46.9nm. In the gas discharge plasma extreme ultraviolet 46.9nm laser experiment, two split vortex spots with opposite topological charges were successfully obtained. Figure 1 shows the results of the 46.9nm vortex focusing experiment, and Figure 2 shows the interference results of the two vortex rotations of the split beam with the reference light. The single cross wire indicates that the topological charge of the vortex rotation is 1, and the cross wire azimuth reflects the opposite chirality of the vortex light. Due to its natural hollow structure, self-supporting irregular photon screens are particularly suitable for short wavelength structural beam splitting control, which provides new development opportunities for future soft X-ray beam splitting vortex control and interference, structural control of high-order harmonic attosecond light, and array sensing imaging.

Figure 1. Focusing experiment of 46.9nm wavelength split vortex, (a) schematic diagram of optical path, (b) vortex focusing spot, (c) full width at half maximum.

Figure 2. Interference measurement of 46.9nm wavelength split vortex, (a-b) simulation results, (c) experimental results.

Relevant work has been supported by the National Natural Science Foundation of China, the Sailing Plan for Young Scientific and Technological Talents in Shanghai, and the Class A project of the Chinese Academy of Sciences' strategic leading science and technology project.

Source: Opticsky