Photonic bandgap structures use the principle of interference to reflect radiation. Reflection from photonic bandgap structures has been demonstrated in one, two and three dimensions and various applications have been proposed. Early work in hollow-core photonic bandgap fibre technology used a hexagonal structure surrounding the air core; this fibre was the first demonstration of light guided inside an air core of a photonic bandgap fibre. The potential benefits of guiding light in air derive from lower Rayleigh scattering, lower nonlinearity and lower transmission loss compared to conventional waveguides. In addition, these fibres offer a new platform for studying nonlinear optics in gases. Owing largely to challenges in fabrication, the early air-core fibres were only available in short lengths, and so systematic studies of loss were not possible. More recently, longer lengths of fibre have become available with reported losses of 1,000 dB km~(-1). We report here the fabrication and characterization of long lengths of low attenuation photonic bandgap fibre. Attenuation of less than 30 dB km~(-1) over a wide transmission window is observed with minimum loss of 13 dB km~(-1) at 1,500 nm, measured on 100m of fibre. Coupling between surface and core modes of the structure is identified as an important contributor to transmission loss in hollow-core photonic bandgap fibres.
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机译：光子带隙结构使用干涉原理来反射辐射。已经从一维，二维和三维中证明了来自光子带隙结构的反射，并提出了各种应用。中空光子带隙光纤技术的早期工作是在空芯周围采用六边形结构。这种光纤是在光子带隙光纤的空芯内引导光的第一个演示。与常规波导相比，在空气中引导光的潜在好处来自较低的瑞利散射，较低的非线性和较低的传输损耗。此外，这些光纤为研究气体中的非线性光学提供了新的平台。由于制造方面的挑战，早期的空心纤维只能以较短的长度使用，因此无法系统地研究损耗。最近，已经出现了更长的光纤长度，据报道损耗为1,000 dB km〜（-1）。我们在这里报告了长长度的低衰减光子带隙光纤的制造和表征。在100m的光纤上测得，在宽传输窗口内的衰减小于30 dB km〜（-1），在1,500 nm处的最小损耗为13 dB km〜（-1）。结构的表面模式和核心模式之间的耦合被认为是导致中空光子带隙光纤中传输损耗的重要因素。
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