Design and optimization of mechanically down-doped terahertz fiber directional couplers

Hualong Bao, Kristian Nielsen, Henrik K. Rasmussen, Peter Uhd Jepsen, Ole Bang

    Research output: Contribution to journalJournal articleResearchpeer-review


    We present a thorough practical design optimization of broadband low loss, terahertz (THz) photonic crystal fiber directional couplers in which the two cores are mechanically down-doped with a triangular array of air holes. A figure of merit taking both the 3-dB bandwidth and loss of the coupler into account, is used for optimization of the structure parameters, given by the diameter and pitch of the cladding (d and Λ) and of the core (dc and Λc) air-hole structure. The coupler with Λ = 498.7 μm, dc= 324.2 μm, Λc = 74.8 μm, and dc = 32.5 μm is found to have the best performance at a center frequency of 1THz, with a bandwidth of 0.25 THz and a total device loss of 9.2 dB. The robustness of the optimum coupler to structural changes is investigated. © 2014 Optical Society of America.
    Original languageEnglish
    JournalOptics Express
    Issue number8
    Pages (from-to)9486-9497
    Publication statusPublished - 2014


    • Photonic crystal fibers
    • Waveguides
    • Terahertz waveguides


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