Abstract
Remarkable recent demonstrations of ultra-low-loss inhibited-coupling (IC) hollow-core photonic-crystal fibres (HCPCFs) established them as serious candidates for next-generation long-haul fibre optics systems. A hindrance to this prospect and also to short-haul applications such as micromachining, where stable and high-quality beam delivery is needed, is the difficulty in designing and fabricating an IC-guiding fibre that combines ultra-low loss, truly robust single-modeness, and polarisation-maintaining operation. The design solutions proposed to date require a trade-off between low loss and truly single-modeness. Here, we propose a novel IC-HCPCF for achieving low-loss and effective single-mode operation. The fibre is endowed with a hybrid cladding composed of a Kagome-tubular lattice (HKT). This new concept of a microstructured cladding allows us to significantly reduce the confinement loss and, at the same time, preserve truly robust single-mode operation. Experimental results show an HKT-IC-HCPCF with a minimum loss of 1.6 dB/km at 1050 nm and a higher-order mode extinction ratio as high as 47.0 dB for a 10 m long fibre. The robustness of the fibre single-modeness is tested by moving the fibre and varying the coupling conditions. The design proposed herein opens a new route for the development of HCPCFs that combine robust ultra-low-loss transmission and single-mode beam delivery and provides new insight into IC guidance.
Highlights
Due to their excellent performance as a platform for the study of fundamental physics and for addressing applied problems in photonics, hollow-core photonic-crystal fibres (HCPCFs) continue to be the subject of intense research since their theoretical proposal in 19951
The results reported demonstrate that the association of two IC claddings can significantly reduce the confinement loss (CL) and modal content in HCPCFs
The results show that when we surround the inner tubes with a Kagome lattice without allowing them to touch, a drop in CL by 5 orders of magnitude relative to a typical tubular or Kagome cladding HCPCF and to the most representative reported HCPCF alternative designs can be achieved
Summary
Due to their excellent performance as a platform for the study of fundamental physics and for addressing applied problems in photonics, hollow-core photonic-crystal fibres (HCPCFs) continue to be the subject of intense research since their theoretical proposal in 19951. These interests are driven by the accomplishment of outstanding results in science, such as atom optics[2] and gas-based nonlinear optics[3], and in industry, such as ultra-shortpulse and high-energy laser beam delivery[4]. Among the noteworthy conclusions of this effort is the fact that for wavelengths shorter than
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