Terahertz orbital angular momentum modes with flexible twisted hollow core antiresonant fiber

Abstract

THz radiation is more and more commonplace in research laboratories as well as in everyday life, with applications ranging from body scanners at airport security to short range wireless communications. In the optical domain, waveguides and other devices to manipulate radiation are well established. This is not yet the case in the THz regime because of the strong interaction of THz radiation with matter, leading to absorption, and the millimeter size of the wavelength and therefore of the required waveguides. We propose the use of a new material, polyurethane, for waveguides that allows high flexibility, overcoming the problem that large sizes otherwise result in rigid structures. With this material we realize antiresonant hollow-core waveguides and we use the flexibility of the material to mechanically twist the waveguide in a tunable and reversible manner, with twist periods as short as tens of wavelengths. Twisting the waveguide, we demonstrate the generation of modes carrying orbital angular momentum. We use THz time domain spectroscopy to measure and clearly visualize the vortex nature of the mode, which is difficult in the optical domain. The proposed waveguide is a new platform offering new perspectives for THz guidance and particularly mode manipulation. The demonstrated ability to generate modes with orbital angular momentum within a waveguide, in a controllable manner, will be beneficial to both fundamental, e.g. matter-radiation interaction, and applied, e.g. THz telecommunications, advances of THz research and technology. Moreover, this platform is not limited to the THz domain and could be scaled for other electromagnetic wavelengths.

Polyurethane Optical Fiber Sensors

“…We have fabricated preforms by stacking polyurethane tubes and drawn them on a (Heathway) draw tower into fibre with a variety of fairly complex geometries (Figure 1). Whilst this is clearly promising for anti-resonant fibres, polyurethane is very challenging to draw and as yet we have not fabricated fibres with thin enough features to operate at short wavelengths (we have realized antiresonant fibres at THz frequencies [1]). However, for many potential applications, sensing over short distances, capillary guidance is adequate.…”

OAM generation, tunable metamaterials and sensors with highly deformable fibers

“…We demonstrated conversion of a fundamental mode to an ℓ=1 OAM mode in an antiresonant guiding fiber in the THz. Taking advantage of THz time domain spectroscopy we measured the vortex nature and evolution of the OAM mode [5], Fig. 1(a).…”

Single‐Step Tabletop Fabrication for Low‐Attenuation Terahertz Special Optical Fibers

“…Indeed, the use of MOFs for the terahertz range is a growing trend. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] Porous-core fibers, for example, have holes within Amid the search for efficient terahertz transmission and gas sensing, all-polymer terahertz waveguides attract significant interest due to their compactness and capability for providing environmentally robust systems. The high loss within metals and dielectrics in the terahertz range makes it challenging to build a low loss, mechanically stable, and broadband terahertz waveguides.…”

“…Indeed, the use of MOFs for the terahertz range is a growing trend. [ 20–33 ] Porous‐core fibers, for example, have holes within the core region, which lessen the overlap between the optical mode and the waveguide material, allowing a reduction loss levels in the terahertz range. [ 5,34–45 ] However, despite all the endeavors toward the development of terahertz fibers with solid or porous cores, achieving low loss, low dispersion, broadband transmission, and ease of fabrication remain critical issues.…”