The theoretical research on fundamental mode 20/400-μm fiber laser for directed-energy application

A theoretical research of fiber laser in single mode operation was presented to evaluate laser targeting characteristics, namely, the directed-energy application. The beam propagation efficiency (BPE) was chosen as the factor to assess the performance of the lasers. Many parameters were studied about their impacts on BPE, including the lens parameters and the transmitting distance. As a result, it was found that the defocus quantity (DQ) valve had a huge impact on directed-energy performance. Given a proper DQ value, the BPE can reach a near limit value. By comparing the BPE performances under different transmission distances, we concluded that when target radius was set to be 5 cm, the ideal state (BPE＞90%) of directed-energy transmission can be achieved within a certain distance of 7 km.