Genetic-algorithm-based design of large-mode-area all-solid anti-resonant fiber with normal dispersion and single-mode operation in the 2 μm wavelength region
Abstract
Recent years have witnessed much progress in the development of fiber lasers in the 2 μm region. Yet, to date, their power levels are limited by modulation instability and soliton formation attributed to the strong anomalous dispersions of fused silica in this wavelength region. Further power scaling requires a novel design of an all-solid silica active fiber that features normal dispersion by compensating the material dispersion with the waveguide dispersion. At the same time, a large mode area, low losses, single mode operation and robustness need to be maintained. In this paper, we propose an all-solid anti-resonant fiber (AS-ARF) design that meets these demands. We demonstrate that normal dispersion can be achieved in AS-ARFs at 2 μm by exploiting the Kramers-Kronig relation. To balance the desired dispersion with the other performance parameters, we optimize the design of the AS-ARFs using a genetic algorithm. The optimized AS-ARF has a mode field area of 1170 μm2 and normal dispersion over the spectrum from 1.96 μm to 2.04 μm. Within this spectrum, the maximum confinement loss (CL) of the fundamental mode (FM) is 16 dB/km and the minimum CL of the higher order modes (HOMs) is over 100 dB/km. The HOMs can be easily coupled out by bending the fiber while the FM stays in the core. For example, the CLs are over 2×104 dB/km for the HOMs and below 200 dB/km for the FM at 2 μm at a bending radius of 20 cm. Moreover, the properties of the proposed AS-ARF remain favorable even under large geometric variations, showing good tolerance to manufacturing errors. We expect the proposed AS-ARF to further stimulate the development of high-power fiber lasers in the 2 μm region.
Md Selim Habib
Assistant Professor of Electrical Engineering
Hollow-core fibers; Fiber sensors; Ultrafast nonlinear optics