Porous-core honeycomb bandgap THz fiber

DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Kongens Lyngby, Denmark.
Optics Letters (Impact Factor: 3.29). 03/2011; 36(5):666-8. DOI: 10.1364/OL.36.000666
Source: PubMed


In this Letter we propose a novel (to our knowledge) porous-core honeycomb bandgap design. The holes of the porous core are the same size as the holes in the surrounding cladding, thereby giving the proposed fiber important manufacturing benefits. The fiber is shown to have a 0.35-THz-wide fundamental bandgap centered at 1.05 THz. The calculated minimum loss of the fiber is 0.25 dB/cm.

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    • "To enable bandgap guidance with low loss while allowing easy fabrication, a porous-core honeycomb bandgap THz fiber (PCHBTF) was proposed in [13] and later demonstrated [5] by the Danish group. Combining a well-studied honeycomb lattice in the optical regime [14]–[17] and a porous core design in the THz field [18]–[21], the PCHBTF has the following advantages [5], [13]: first, the cladding PBG structure is based on a honeycomb lattice, which is known [14]–[17] to allow broad bandgaps for smaller air holes than the triangular lattice; second, although not guiding in air, the porous core containing a significant number of air holes is still able to reduce the loss compared to a solid core; finally, the air holes in the core and cladding have the same size, making fabrication easier. However, the composite porous core of the PCHBTF makes the fiber design complicated and mode classification for this fiber also needs to be investigated . "
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    ABSTRACT: We describe a semi-analytical approach for modeling fibers which guide THz radiation in a porous core by the photonic bandgap effect due to a honeycomb cladding of air holes. These porous-core honeycomb bandgap THz fibers (PCHBTFs) are modeled as equivalent step-index fibers (SIFs). The effective core index of the SIFs can be solved analytically as that of the fundamental space-filling mode of the triangular lattice comprising the porous core. The cladding index is taken as that of the bandgap edge with the lower index and is computed numerically. The validity of the analogy between PCHBTFs with SIFs is established by comparing the mode profiles, mode number, mode indices, and the fraction of mode power in the core obtained for a 19-cell core multimode THz fiber by the semi-analytical theory with results by finite element method. The subtle difference in mode degeneracy of the PCHBTFs and SIFs is briefly discussed. The semi-analytical theory also predicts that a seven-cell core PCHBTF is effectively single mode with higher-order modes pushed close to the bandgap edge.
    Full-text · Article · May 2015 · Journal of Lightwave Technology
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    • "Use of a porous core is resulted in reduction of quantity of solid material in the core as well as the absorption loss. Efficient honeycomb band-gap fibers were reported [23] [24], where porous core PCFs were investigated both numerically and experimentally . Also, a hexagonal PCF with hexagonal porous core (hexa-core) was reported [25] with a low absorption loss (0.12 cm "
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    ABSTRACT: A kind of porous core photonic crystal fiber (PCF) for terahertz (THz) wave propagation is proposed in this paper. By intentionally rotating the porous core lattice structure, a dispersion of 1.06 ± 0.12 ps/THz/cm in a frequency range of 0.5–1.08 THz is observed. Also, a very low material absorption loss (0.066 cm−1) and low confinement loss (4.73 × 10−4 cm−1) at the operating frequency f = 1 THz are obtained. Besides, single-mode properties, power fraction in air core and frequency response of the proposed PCF are also analyzed. The reported design can be fabricated easily using stack and draw method and be used in potential applications in the THz region.
    Full-text · Article · May 2015 · Optical Fiber Technology
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    • "Because of the high absorption losses in dielectrics, a large amount of work has been driven to study a variety of guiding mechanisms to reduce the propagation losses for terahertz radiations. Given that dry air is almost transparent for terahertz wave propagation, many optical-fiber-type guiding designs have been developed with the main aim to force a large part of the terahertz radiation to propagate in air while still confine it to a waveguide, these include, for example, subwavelength dielectric fibers [9]–[11], hollow-core fibers [12]–[15], porous fibers [16], [17], porous-core bandgap fibers [18], [19] and suspended core subwavelength fibers [20]. "
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    ABSTRACT: We propose the design of a low-loss suspended core terahertz fiber with rectangular-shaped dielectric strips in the fiber cross section. The finite element method is used to analyze the characteristics of the suspended core terahertz fiber. Terahertz wave in a frequency range from 0.74 ~ 0.95 THz is efficiently confined in the suspended core region with a total loss lower than 0.086 dB/cm ( ~ 0.02 cm-1). Meanwhile, any contact on the surface of this fiber will not disturb the field and induce additional losses. A 3.36-cm-long terahertz polarization splitter derived from this fiber with a transmission loss less than 0.89 dB, is also numerically demonstrated. A bandwidth of 0.032 THz at the center frequency of 1 THz with an extinction ratio better than -20 dB is obtained.
    Full-text · Article · Dec 2013 · IEEE Photonics Journal
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