Abstract

A comprehensive characterization of the diffraction properties of terahertz (THz) pulsed broadband vortex beams consisting of several electromagnetic field oscillations requires state-of-the-art techniques for studying the evolution of a wavefront as it propagates. For this purpose, we have applied the capabilities offered by THz pulse time domain holography. Accurate metrological study of pulsed single-period THz field propagation allowed us to reveal the spatio-temporal and spatiospectral couplings in broadband uniformly topologically charged vortex beams. Here, we reveal dynamics of such beam propagation in a free space as well as in the experiment with edge diffraction with 50% blocking of the beam focal waist. In this study, we compare the dynamics of freely propagating and edge-diffracted THz vortex. Despite the fact that in the amplitude representation one can observe the emergence of strong asymmetry, analysis of the spectral trajectory of the singular point at some distance from the obstacle and the visualization of phase distribution for individual spectral components testify to the conservation of transverse energy circulation. Similar to the edge diffraction of monochromatic optical vortices, it can be interpreted as self-reconstruction of vortex properties. The given term has not previously been used for the case of pulsed broadband THz beams, to the best of our knowledge.

© 2018 Optical Society of America

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References

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Supplementary Material (8)

NameDescription
» Visualization 1       Time sweep of THz BUTCH vortex beam cross-section upon generation
» Visualization 2       Frequency sweep of the THz BUTCH vortex beam phase at generation
» Visualization 3       Time sweep of THz BUTCH vortex beam cross-section in the focal spot
» Visualization 4       Time sweep of THz BUTCH vortex beam cross-section 25 mm after the focal spot
» Visualization 5       Time sweep of half-blocked Hz BUTCH vortex beam cross-section in the focal spot
» Visualization 6       Time sweep of THz BUTCH vortex beam cross-section after diffraction on the half-blocking screen, 25 mm after focal plane
» Visualization 7       Frequency sweep of the THz BUTCH vortex beam phase 25 mm after the focal plane
» Visualization 8       Frequency sweep of the THz BUTCH vortex beam phase 25 mm after diffraction on half-blocking screen in the focal plane

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Equations (13)

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