Preparation and performance study of a Tm3+-doped silicate heterogeneous helical cladding large mode area fiber

Abstract

Tm³⁺-doped fiber lasers are widely used in industrial manufacturing, medical treatment and national defense fields et al. In this work, a Tm³⁺-doped silicate glass large mode area fiber with heterogeneous helical claddings was fabricated for the first time, including glass preparation, fiber preparation and testing, etc. Refractive index of the core, inner cladding 1 (and outer cladding) and inner cladding 2 are 1.51826, 1.51745 and 1.51838 respectively. The difference of T_g (T_s or α_20-300) between core and cladding glass is very small and meets the requirements of fiber drawing. The structure parameters of the prepared fiber are as follows: the core diameter is 60 μm, the outer cladding diameter is 298.29 μm, the helix pitch is 25 mm and the central angle of cladding 2 is 15.66°. The mode transmission characteristics of the fiber was tested, and the output spot of the fiber was close to a single-mode state, which is basically consistent with theoretical design results. The loss and net gain coefficients of the fiber are 2.88 dB/m and 0.366 dB/m, respectively. The loss coefficient is high, the reasons and improvement methods have been provided. The relevant exploration is conducive to promoting the further application of this new type of optical fiber.