Low Loss Hollow-Core Antiresonant Fiber With Nested Elliptical Cladding Elements

Abstract

We design and investigate the optical properties of a novel hollow-core antiresonant fiber with nested elliptical cladding elements. This new structure shows low confinement loss even with a relatively small core. The lowest confinement loss of this structure is more than two orders of magnitude smaller than its circular-element counterparts. When the size of the cladding elements is properly designed, higher order core modes resonantly couple with the cladding modes effectively, resulting in an extremely high higher order-mode extinction ratio ( $>$ $10^4$ ). This good single mode performance can be achieved for a wide range of cladding element parameters, which would increase the fabrication tolerance. The new fiber also shows low bending loss for a wide range of bend radii. Moreover, dispersion properties of the new structure are also investigated under both unfilled and filled conditions. Numerical results show that antiresonant structures with the same core diameter and strut thickness have similar dispersion curves. The zero dispersion wavelength within the fundamental antiresonant transmission band can be tuned over tens of nanometers by increasing the pressure up to 50 bar when the fiber is filled with argon.