Abstract
We propose a novel design of hollow-core fiber for enhanced light guidance in the mid-infrared. The structure combines an arrangement of non-touching antiresonant elements in the air core with a multilayer glass/polymer structure in the fiber's cladding. Through numerical modeling, we demonstrate that the combination of antiresonant/inhibited-coupling and photonic bandgap guidance mechanisms can decrease the optical loss of a tubular antiresonant fiber by more than one order of magnitude. More specifically, our simulations demonstrate losses of the HE11 mode in the few dB/km level, which can be tuned through mid-infrared wavelengths (5 µm-10.6 µm) by carefully optimizing the structural parameters of both structures. We also show that the hybrid hollow-core fiber design is more robust to bend-induced loss than an equivalent tubular antiresonant fiber or a Bragg/OmniGuide fiber. As a result, if successfully fabricated, the hybrid hollow-core fiber will offer low-loss, high beam-quality, effectively single-mode operation, and low bending losses, potentially solving many of the problems that affect all known mid-infrared fiber types.
Highlights
Hollow-core fibers have been the focus of much interest lately due to their ability to guide light in the air core rather than in a solid material
For light guidance in the near-infrared, it has been shown that adding additional radial membranes/nested tubes in antiresonant hollow-core fibers (AR-HCF) helps reducing leakage loss [12,14], which dominates their overall loss
We propose a different approach to reduce leakage loss in MIR AR-HCFs that does not require the employment of nested tubes [12] or conjoined elements [14]
Summary
Hollow-core fibers have been the focus of much interest lately due to their ability to guide light in the air core rather than in a solid material. For light guidance in the near-infrared, it has been shown that adding additional radial membranes/nested tubes in AR-HCFs helps reducing leakage loss [12,14], which dominates their overall loss This can be done controllably with silica AR-HCFs, but becomes increasingly difficult to achieve for fibers made of MIR transmitting glasses, such as tellurite, chalcogenide, and fluoride. Design combines a tubular antiresonant structure with a multilayer Bragg cladding This hybrid fiber confines the light in the hollow-core simultaneously by antiresonant and photonic bandgap mechanisms. We show that this is possible and such combination can achieve a novel fiber design that incorporates the best properties of both worlds, namely the effective single-mode operation, the extremely low overlap of the fundamental optical mode with the cladding material, broadband operation, low non-linearity, high beam-quality and low straight and bending losses.
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