Design and performance study of a Tm-doped 4 × 4 square array polarization-maintaining large-mode-area fiber

Laser coherent beam combination technology based on uncoupled multicore fibers has achieved many breakthrough results in recent years. To improve the efficiency and power of laser coherent beam combination. This paper designed a thulium-doped 4 × 4 square array polarization-maintaining large mode area fiber for the first time. Each core is surrounded by air holes and stressed by two symmetrical circular stress regions, as a result, polarization-maintaining characteristics and single-mode operation have been implemented, and the mode field area of each core reaches 246.84 μm². The minimum FM loss for X-polarization is 3.14 dB/m, the maximum FM loss for Y-polarization is 0.1 dB/m, and the minimum LP₁₁ mode loss is 18.44 dB/m. These results show that the thulium-doped 4 × 4 array polarization-maintaining and large-mode-field fibers can be applied in laser coherent polarization combination systems to achieve higher combination efficiency.