Segmented Cladding Fiber With a High-Index Ring in Core for Wideband Single-Mode Operation in Any Bending Orientation

Abstract

A resonant-ring-assisted large mode area segmented cladding fiber (RR-SCF) with a high-index ring in the core is proposed. Numerical investigations of the effects of the high-index ring on the leakage losses of guiding modes, mode area, and electric field distribution of FM in the proposed fiber show the high-index ring not only increases the ratio of the loss between the fundamental mode (FM) and the higher-order modes (HOMs) but also improves the electric field distribution of the FM to be flat. By taking these advantages of the high-index-ring-assisted core, the effective single-mode (SM) operation is achieved in the proposed fiber bent in any orientation, which makes up the defect of the conventional RR-SCF that the SM output is affected by the bending orientation. Meanwhile, the mode area is enlarged. Furthermore, the effects of the heat load, duty cycle, bending, and operation wavelength on the fiber performance are analyzed. The results show single-mode operation in all bending orientations with a mode area larger than 824 μm 2 can be achieved at a tight bending radius of 15 cm to 16 cm when the operating wavelength ranges from 1.06 μm to 1.76 μm. This fiber shows great potential in high-power fiber lasers.

A Large Mode Area Parabolic-Profile Core Fiber with Modified Segmented in Cladding

“…The heat load will influence the equivalent refractive index of the proposed fiber. The relationship between heat load and refractive index can be calculated as [39]:…”

Investigating changes in the electric field profiles of transverse modes in fibres due to bending

“…Prior to this, reports have been presented in the field of the electric field of beams inside fibres, encompassing spatial distribution of the mode fields of both straight and bent fibres. Additionally, valuable experimental and theoretical works on this subject, including the analysis of beam modes, have been published [25][26][27][28][29][30][31]. Also, due to reasons such as microscopic bends, voids and cracks, the variation in the diameter and density fluctuation, the transition from one mode to another mode during propagation in the fibre is possible.…”