Beam quality factor of ring-assisted fiber

Abstract

Ring-assisted fiber (RAF) introduces a high refractive index ring into the cladding of the fiber, which brings the fiber more flexibility for communication and high-power application. In this paper, for the first time, we investigate how the additional ring affects the beam quality factor. The theoretical optical field model of RAF is established and verified at the first step. Then both the M2 factor and the β factor under different cases are numerically calculated, based on their general definition and the theoretical filed model. The results show that a larger thickness of the ring will greatly deteriorate the beam quality, but the distance between the ring and the core of RAF brings little influence on the beam quality. Besides the ring parameters, the beam quality factors of the pure and mixed modes under different wavelengths are also investigated systematically. Our results will not only provide a comprehensive understanding on the beam quality of RAFs, but also offer a guide to the design of this novel fiber for further applications.