Design of Broadband Porous-Core Bandgap Terahertz Fibers

Fibers that operate by the photonic bandgap effect guide light only within a limited frequency range and broadband transmission is highly desirable for the terahertz (THz) frequency range. A semi-analytical approach is used for the design of broadband porous-core bandgap THz fibers based on a honeycomb and Kagome lattice of air holes. We show how the design approach allows a fast and accurate determination of the mode indices for different sizes of the core air holes. In particular, a reduction of the central air hole size from that of the cladding air holes allows both fibers to operate within the first bandgap, enabling broadband transmission within the frequency range of 0.7-2 THz. These fibers will be promising for THz wave transmission.