Optimization of hollow-core fibers with elliptical tubes for improved single-mode guidance

Abstract

Hollow core fibers with elliptical tubes offer more design flexibility and can achieve better performance compared to their circular counterparts. We optimize the elliptical tubes of a hollow-core fiber to achieve a higher order mode extinction ratio (HOMER) exceeding 5500 along with a confinement loss of 0.012 dB/m in the telecommunication band; 4.7×10−4 dB/m with HOMER > 4300 in the visible band. We also derive an empirical relation between the structural parameters to obtain avoided crossings between the core higher order modes and the cladding modes to achieve the best single-mode guidance, besides achieving minimum confinement loss for the fundamental mode. We investigate the effect of bends on not just the confinement loss, but also on the HOMER. We have also included the dispersion and fabrication tolerances. These fibers find applications in quantum communication, sensing, and high-power laser delivery.