Abstract

Single-ring hollow core photonic crystal fibre (SR-PCF) has created much interest over the past several years because of the simplicity of the structure, relatively low transmission losses and broad guidance bands. SR-PCF consists of a ring of thin-walled capillaries (inner diameter d) arranged symmetrically around a central hollow core (diameter D). It has been shown that if d/D = 0.682, the LP₀₁-like core mode is strongly confined by anti-resonant reflection at the capillary ring, whereas higher order modes (HOMs), such as the LP₁₁-like mode, are resonant with the capillaries and leak strongly away [1]. This condition for HOM suppression can be tuned by spinning the fibre preform during drawing, so as to produce a helical structure. This extends the length of the spiralling capillaries, slowing down the axial speed of the light and permitting HOM suppression at values of d/D < 0.682 [2].

© 2017 IEEE