![]() ![]() THz communication systems were developed on the basis of continuous and narrow-band THz signal sources. ![]() THz communications are a promising technology to satisfy the increasing requirements on a capacity and speed of data transmission in wireless systems 10, 11, 12. Another actively developing application based on THz radiation is THz communications, where the Bessel beam’s potential for wireless communications was studied 9. ![]() For example, usage of Bessel-like beams in THz imaging results in significantly improved depth of focus 8. Recently, studies of terahertz (THz) Bessel beams properties began, and Bessel beams of narrow and broadband THz radiation have already found their application in several fields. The concept of non-diffractive beams can be theoretically implemented for any range of electromagnetic radiation. Quasi-Bessel beams are widely used in optical coherence tomography 3, control of micro- and nanoparticles 4, high-precision microprocessing 5, detection of rotating objects 6 and three-dimensional imaging 7. Quasi-Bessel beams are also actual in case of non-linear light-matter iteractions: these beams enhance ionization and laser-induced plasma effects 2. Incident radiation can be both continuous wave or pulsed wave.Īt present, quasi-Bessel light beams attract wide attention from scientists due to a number of unique properties 1: high intensity in the near-axis region over a limited propagation distance, small diffraction divergence of the central maximum in comparison with traditional Gaussian beams, and reconstruction properties. A Gauss-Bessel light beam is generated at the axicon exit with an amplitude distribution in the radial cross-section described by the square of the zeroth-order Bessel function. Gauss-Bessel beam formation by the axicon occurs due to a linear phase-delay in a transverse coordinate for an incident light field. One of the most efficient ways for quasi-Bessel beams generation is Gaussian beam focusing by an axicon or conical lens. The beams obtained in such approximations are called quasi-Bessel beams and exhibit low or no diffraction over a limited propagation distance. ![]() Although true non-diffractive Bessel beam can not be created in practice, several approximations can be made. Results of the phase velocity calculation depend strongly on distance increment value, thus demonstrating superluminal or subluminal behavior.īessel beam is a theoretical model of non-diffracting light beam with an infinite number of rings that can cover an infinite distance and require an infinite amount of power. Phase velocity via propagation distance is estimated and compared with existing experimantal results. The spatio-temporal and spatio-spectral profiles for different spectral components clearly illustrate the model where the Bessel beam’s wavefront at the exit from the axicon can be divided into radial segments for which the wave vectors intersect. This behavior illustrates strong spatio-temporal coupling effect when spatio-temporal distribution of Bessel beam’s wavefront depends on propagation distance. The reshaping is also illustrated by the energy transfer dynamics, where the pulse energy flows from leading edge to trailing edge. We have characterized two-dimensional spatio-temporal beam behavior and demonstrated all stages of pulse reshaping during the propagation, including X-shape pulse forming. We have numerically analyzed pulsed broadband terahertz Gauss-Bessel beam’s both spatio-temporal and spatio-spectral evolution in the non-paraxial approach. Terahertz pulse time-domain holography is the ultimate technique allowing the evaluating a propagation of pulse broadband terahertz wavefronts and analyze their spatial, temporal and spectral evolution. ![]()
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