Low loss porous terahertz fibers containing multiple subwavelength holes

Abstract

We propose a porous polymer terahertz fiber with a core composed of a hexagonal array of subwavelength air holes. Numerical simulations show that the larger part of guided power propagates inside the air holes within the fiber core, resulting in suppression of the bulk absorption losses of the core material by a factor of ∼10–20. Confinement of terahertz power in the subwavelength holes greatly reduces effective refractive index of the guided mode but not as much as to considerably increase modal radiation losses due to bending. As a result, tight bends of several centimeter bending radii can be tolerated.

Bendable, low-loss Topas fibers for the terahertz frequency range

“…We show near-field images of the electric field amplitude and phase of the propagating mode in a photonic crystal fiber, visualizing single-mode propagation over a wide frequency range, the onset of higherorder mode propagation at high frequencies, and indication of the predicted porous guiding at low frequencies and high porosity [6,7,8,9].…”

“…Parallel to the impressive development of THz sources and detectors there has been significant development of new concepts for guided propagation of THz fields. Examples include dispersive propagation in square and circular metallic waveguides [10] Hassani et al [6,7] and independently Atakaramains et al [8,9] recently proposed a novel guiding mechanism with high confinement of the guided mode in the core of an sub-wavelength diameter air-clad step-index fiber (a thin wire) with a distribution of sub-wavelength holes inside the wire. The field in such porous THz fibers is locally enhanced in the air holes.…”

Broadband terahertz fiber directional coupler

“…However, both fibers were subwavelength-sized rod-in-air type fibers [2][3][4][5]7,12]. The advantage of such a rod-in-air fiber is that the THz field has a small overlap with the lossy waveguide material.…”

“…Consequently, there are now several demonstrated THz frequency waveguide concepts [2][3][4][5][6][7][8][9][10][11][12][13]. As the waveguides increase in quality, the next step is to make functional THz waveguide devices.…”

Ultra low bending loss equiangular spiral photonic crystal fibers in the terahertz regime

“…The latter often utilize a 'drill and draw' 5,6 or 'stack and fuse' 4 technology in their fabrication. Recently, very low loss operation in a PCF made from Topas R polymer has been demonstrated 5 and a new class of porous fibers have also been reported, [7][8][9] though achieving high porosity is not trivial. 9 In this letter, an Equiangular Spiral (ES) PCF design inspired by nature 10,11 in Topas R is presented for THz frequencies.…”