Diffraction of terahertz waves after passing through a Fresnel lens |
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| Authors: | Shi Yu-Lei Zhou Qing-Li and Zhang Cun-Lin |
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| Affiliation: | Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048, China |
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| Abstract: | The spatiotemporal and spectral characteristics of
ultrawide-band terahertz pulses after passing through a Fresnel lens
are studied by using the scalar diffraction theory. The simulation
shows that the transmitted terahertz waveforms compress with
increasing propagation distance, and the multi-frequency focusing
phenomenon at different focal points is observed. Additionally, the
distribution of terahertz fields in a plane perpendicular to the
axis is also discussed, and it is found that the diffraction not
only induces focusing on-axis but also inhibits focusing at off-axis
positions. Therefore, the Fresnel lens may be a useful alternative
approach to being a terahertz filter. Moreover, the terahertz pulses
travelling as a basic mode of a Gaussian beam are discussed in
detail. |
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| Keywords: | terahertz Fresnel lens diffraction field |
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