Fabrication Of Pump Coupler Based On Thermally Expanded Core Fiber Technology

Pump coupler as a key passive component in fiber laser system, it commonly used to coupler the pump light into dual cladding fiber efficiently. It's performance determinate the output power of fiber laser. In traditional process of fabricating pump coupler, the mode field mismatch between the signal and the output fiber induces the signal loss, which restrict the input power of signal light. In order to solve this problem, we use thermally expanded core fiber technology to make the mode field size of the signal fiber match the output fiber. In this article, we fabricated a type of pump coupler based on the thermally expanded core fiber technology, meanwhile, we studied the coupling efficiency in theory and experiment. This dissertation mainly includes four sections.1. The first section is simulation, geometrical optics and beam propagation method were used to analyze the relationship of the parameters in pump coupler. In addition, we built the pump fiber twisting model and did some numerical calculations.2. After matering several fibers arrangement, fiber bundle tapering, fiber bundle cleaving, low loss fusion technology, we fabricated pump combiner. Meanwhile, we tested the pump and signal fiber transmitting efficiency. Furthermore, we used mode integral principle calculate the transmission loss between two fibers. The mode field mismatch results the large signal loss, the simulation results show excellent agreement with the experimental results.3. We raised and realized the pump combiner fabrication based on thermally expanded core fiber technology. Firstly, we introduced the thermally expanded core fiber technology theoretically. Then, we raised the pump combiner fabrication based on thermally expanded core fiber technology. Finally, we fabricated the pump combiner based on this method. The pump coupling efficiency ranged from 96% to 99%. The signal coupling efficiency increased from 50% to 93.48% through testing compared with the former pump coupler. The results sufficiently verified that the expanded core fiber technology can improve the transmitting efficiency. This method could provide the key component in high power fiber amplifier.