Abstract
Waveguiding mechanism and modal characteristics of hollow core fibers consisting of a single or a regular arrangement of dielectric tubes are investigated. These fibers have been recently proposed as low loss, broadband THz waveguides. By starting from a description in terms of coupling between air and dielectric modes in a single tube waveguide, a simple and useful model is proposed and numerically validated. It is able to predict dispersion curves, high and low loss spectral regions, and the conditions to ensure the existence of low loss regions. In addition, it allows a better understanding of the role of the geometrical parameters and of the dielectric refractive index. The model is then applied to improve the tradeoff between low loss and effectively single mode propagation, showing that the best results are obtained with a heptagonal arrangement of the tubes.
Highlights
Development and enhancement of low loss waveguide covering the electromagnetic spectrum from 300GHz and 30THz, have been driven by a growing interest in Terahertz (THz) technology [1]
Compared to photonic band gap fibers (PBGFs), these fibers exhibit much broader low loss regions alternate with high loss regions, and they are called broadband hollow core (HC) fibers (BHCFs)
In this paper the waveguiding mechanism in hollow core fibers composed by a single dielectric tube or a regular arrangement of tubes has been thoroughly analyzed
Summary
Development and enhancement of low loss waveguide covering the electromagnetic spectrum from 300GHz and 30THz, have been driven by a growing interest in Terahertz (THz) technology [1]. Numerical analysis has shown that this fiber falls into the class of the BHCFs [24] It exhibits very interesting properties such as transmission bandwidth of several hundreds of GHz, low loss, low dispersion and high coupling efficiency with free space propagating beams [24], [25]. Since both kagome and square lattice can be seen as an intersection of slab waveguides of infinite width, the resonance frequencies are approximated by the transverse resonance condition [29], corresponding to cut-off frequencies of slab modes These models are unable to explain some important features of transmission spectrum such as the high loss region at low frequencies and the bandwidth of the high loss regions.
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