Propagation dynamics of ultrabroadband terahertz beams with orbital angular momentum for wireless data transfer

Abstract

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Design of broadband terahertz vector and vortex beams: I. Review of materials and components

“…One of the most promising candidates for achromatic devices in the broad frequency range are devices based on total internal reflection (TIR), as there are plenty of materials with flat refractive index dispersion in the THz range 133 . Among the achromatic TIR components developed to date for the THz range, one can find Fresnel prisms 33,133,112 (Fig. 3b 4 ) and non-axially symmetric wave ) and a 2 the image of sectorial chromatic q-plate (the photo was courtesy provided by Emmanuel Abraham).…”

“…Ultrashort pulses possessing a homogeneous vortex structure across broad spectral range are known as broadband uniformly topologically charged (BUTCH) 26 beams and belong to the class of topological charge dispersion-free beams 27−32 . Such beams in THz frequency range are already finding unique applications, e.g., as sensors of magnetic properties 33 , or as a carrier in the information encoding 34−37 . The formation of these beams is a complicated task due to the necessity to provide a homogeneous cyclic phase swirl for a large number of dispersive spectral components.…”

Design of broadband terahertz vector and vortex beams: II. Holographic assessment

“…Vortex and vector terahertz (THz) beams [1] became quite a hot topic in the last decade due to their importance for wireless data transfer multiplexing [2,3,4], imaging [5], including visualisation in highly scattering and absorbing media [6], ultrafast current and (de)magnetisation processes probing [7] and even waveguide electron acceleration by a longitudinal polarisation mode [8,9]. Despite the growing application-driven demand for shaped vector and vortex beams [10], especially for ultrafast THz radiation, the amount of approaches to formation and generation, as well as the number of techniques to conveniently assess and characterise such beams is rather limited since they were mainly adopted from the visible range [11].…”

Single-scan multiplane phase retrieval with a radiation of terahertz quantum cascade laser

“…In this field, THz imaging [1][2][3] represents one of the most promising approaches, since it provides spatially resolved information about the investigated objects. THz phase imaging (THz PI) [4,5], which includes pulse time-domain holography (PTDH) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] as well as continuous wave (CW) holography [23][24][25][26][27][28][29][30], Hartmann wavefront sensing [31][32][33][34][35], shearorgaphy [36], ptychography [37][38][39][40][41], and other phase retrieval techniques [42][43][44][45][46][47][48][49], ...…”

“…A lot of technical solutions, experimental layouts, and reconstruction algorithms for THz PI have been proposed, and this field is reaching a certain level of maturity [5]. THz PTDH provides ultimate opportunities to track the dynamics of all the characteristics of a broadband THz field in spatial, temporal, spectral, and angular coordinates [50] during its interference [18,19,21] and propagation, both in free space [9,12,17,22], through designed optical elements [51], obstacles [13,20], and investigated objects [8,10,11,16]. THz wavefront characterization with subsequent compensation through adaptive optics also serves as a compelling use case [52].…”