Influence of directivityof bars on pump-couplingin hollow duct

To get the best results in the simulation of designing a hollow-duct pump-coupling system, we measured the actual directivity of bars of laser diode arrays. Compared to the model with an ideal directivity of bars, the decrease in the coupling efficiency is as large as 11.2% in our model with the actual directivity of bars. A larger transmission loss and a worse intensity distribution of the pump field are got at the same time. The results of the simulation are well matched with that of the experiment. It is concluded that simulating with the actual directivity of bars is essential and more accurate.