A terahertz multimode broadband tuned vortex beam radiation source and its control method

Abstract

The invention discloses a terahertz multimode broadband tuned vortex beam radiation source and a control method thereof. The invention adopts the method of vacuum electronics to coaxially connect the cylindrical grating, the metal cylinder and the spiral grating into a whole in order to directly generate the terahertz vortex beam, which avoids the problems of lack of terahertz devices and the diffraction of terahertz wave intensity. The terahertz beam source and the two-stage structure in which the terahertz beam is converted into a vortex beam are integrated together to directly form a terahertz vortex beam source; the present invention only needs an annular cathode and a static magnetic field, and does not require a complicated feed circuit The terahertz vortex beam produced by the present invention can work in the ultra-wideband range; the present invention can realize mode tuning and beam scanning of the terahertz vortex beam in the broadband range; the vortex beam produced by the present invention The handedness is only related to the handedness of the helical periodic structure, and the generated vortex beam is very robust.

Description

technical field [0001] The invention relates to vortex beam technology, in particular to a terahertz multimode broadband tuned vortex beam radiation source and a control method thereof. Background technique [0002] A vortex beam is a special electromagnetic wave with a helical phase front. Since its discovery, it has aroused widespread interest and plays an important role in the fields of optical manipulation, electromagnetic imaging, sensing and communication. In the terahertz band, vortex beams can also be applied in terahertz communication, super-resolution imaging, spectroscopy detection, electron acceleration and other fields. However, limited by the development of terahertz devices and terahertz sources, how to efficiently excite broadband tunable multimode vortex beams in the terahertz band has not been effectively solved. At present, vortex beams can be generated in the terahertz band through structures such as spiral phase plates, metasurfaces, holographic phase p...

AI Technical Summary

Problems solved by technology

However, limited by the development of terahertz devices and terahertz sources, how to efficiently excite broadband tunable multimode vortex beams in the terahertz band has not been effectively solved.

At present, vortex beams can be generated in the terahertz band through structures such as spiral phase plates, metasurfaces, holographic phase plates, liquid crystals, and array antennas, but these methods still have the following problems to be solved: 1. Once the parameters of the structure are determined, The vortex mode of the vortex beam generated by the device is difficult to adjust, which is not conducive to the application of multi-mode vortex beams; second, these devices manipulate and transform the existing terahertz beams, due to the lack of terahertz devices and the The wave has a relatively strong diffraction effect, and these methods cannot produce a terahertz vortex beam with high purity; 3. Since the metasurface structure works based on the principle of resonance, it can only work near the resonance point and has a narrow working bandwidth; 4. 1. The radiation direction of the vortex beams excited by these structures is difficult to adjust; 5. For array and antenna structures, the feeding network is complex and bulky, and it is not easy to achieve a compact structure

The OAM mode radiator provided in Chinese Patent Application No. 202010357771.1 is a broadband vortex beam radiator that works based on the principle of artificial surface plasmons, and the energy fed by the feed source will be on all frequency points of the radiated vortex beam Nearly uniform distribution, it is impossible to achieve precise energy conversion at a single frequency point, and there is a problem of spectrum energy divergence

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