Genetic-Algorithm-Based Design of Large-ModeArea All-Solid Anti-Resonant Fiber With Normal Dispersion and Single-Mode Operation in the 2 mu m Wavelength Region

Recent years have witnessed much progress in the development of fiber lasers in the 2 mu m 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 mu m 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 mu m(2) and normal dispersion over the spectrum from 1.96 mu m to 2.04 mu m. Within this spectrum, the maximum confinement loss (CL) of the fundamental mode (FM) is 16 dB/km and theminimum CL of the higher order modes (HOMs) is over 100 dB/km. TheHOMscan be easily coupled out by bending the fiber while the FM stays in the core. For example, the CLs are over 2x10(4) dB/km for theHOMsand below200 dB/km for the FM at 2 mu m at a bending radius of 20 cm. Moreover, the properties of the proposedAS-ARFremain 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 mu m region

Automated summary

This study proposes a novel design of an all-solid anti-resonant fiber (AS-ARF) that achieves normal dispersion at 2 μm wavelength for high-power fiber lasers. The AS-ARF design is optimized using a genetic algorithm to balance dispersion, mode field area, and confinement loss. The optimized AS-ARF demonstrates favorable properties such as normal dispersion over a wide spectrum, large mode field area, low losses, and tolerance to manufacturing errors.