Abstract
Based on the complementary V-shaped antenna structure, ultrathin vortex phase plates are designed to achieve the terahertz (THz) optical vortices with different topological charges. Utilizing a THz holographic imaging system, the two dimensional complex field information of the generated THz vortex beam with the topological number l=1 is directly obtained. Its far field propagation properties are analyzed in detail, including the rotation, the twist direction, and the Gouy phase shift of the vortex phase. An analytic Laguerre-Gaussian mode is used to simulate and explain the measured phenomena. The experimental and simulation results overlap each other very well.
Highlights
As special light beams, vortex beams are always interesting members in optics, which possess helical wavefronts, an on-axis phase singularity, and quantization orbital angular momentums [1,2,3]
In 2013, we extended the structure into the THz wave band and fabricated ultrathin THz lenses and phase holograms [33]
After the THz wave passing through the vortex phase plate (VPP), the transmitted THz vortex beam with a vertical polarization impinges on the sensor crystal
Summary
Vortex beams are always interesting members in optics, which possess helical wavefronts, an on-axis phase singularity, and quantization orbital angular momentums [1,2,3]. As a novel far infrared radiation, the terahertz (THz) ray has become a hot topic of optical researches in the past decades and the THz technology has exhibited strong application potentials in many imaging and sensing fields [20,21,22,23]. Genevet et al utilized the design to build a vortex phase plate (VPP) and generate an optical vortex in the infrared wave band [32]. The complementary V-shaped antenna structure is applied to mold ultrathin VPPs in the THz wave band. Utilizing a THz holographic imaging system, the complex field information of the generated THz vortex beam with the topological number l = 1 is coherently measured and its far field propagation properties are investigated in detail. This work prompts the development of ultrathin THz elements and investigations on the THz vortex beams
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