Single air-hole ring polygonal photonic crystal fibers with reduced bending loss and field distortion

In the present paper large mode area polygonal photonic crystal fibers with a single air-hole ring, which can be exploited for high-power fiber laser applications, have been studied. A new design that structures the air-holes in a single ring, according to a polygonal symmetry, around a solid core has been proposed. Octagonal and decagonal symmetries have been considered to design fibers less affected by the penalties arising in bending conditions, in particular the loss and the guided mode field distortion. The bending properties of different fibers with an effective area of 1400 mum², confinement loss lower than 0.3 dB/m for the fundamental mode, and about 1 dB/m for the first higher order one at 1064 nm, have been analyzed and compared. Simulation results have shown that the mode distortion, evaluated through an overlap factor on a circular core region, as well as the loss value, can be reduced when considering photonic crystal fibers with a decagonal symmetry.