Optical Properties of Low Loss (70dB/km) Hypocycloid-Core Kagome Hollow Core Photonic Crystal Fiber for Rb and Cs Based Optical Applications

We report on hypocycloid core shaped hollow-core Kagome fiber with a record loss of 70 dB/km at a spectral range of around 750–850 nm, which is compatible with Cs and Rb based applications. The fiber exhibits a single mode operation in a core diameter as large as <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$40~ \mu{\rm m}$</tex></formula> , and very low sensitivity to bend. We show experimentally that the bending-loss is limited by coupling between the guiding core mode and the modes in the cladding holes.