Transmission Matrix-Inspired Optimization for Mode Control in a 6 x 1 Photonic Lantern-Based Fiber Laser

A photonic lantern is a coherent beam combination device that can increase the fiber laser brightness by adaptively controlling the input light properties, such as phase, intensity, and polarization. However, the control effect is closely related to the initial optical field, which affects the convergence speed to obtain the optimum solutions. In this work, we propose a novel control strategy using the prior structural information of the photonic lantern. Taking a 6 x 1 photonic lantern as an example, we calculate the transmission matrix of the photonic lantern. The initial optical field conditions, fed as the control inputs, for various mode outputs can be obtained. Compared with the random and equal amplitude control methods, the preset method from the transmission matrix presents a significant improvement of the desired mode content. Our optimization method is generally useful for adaptive control systems to improve their performance, taking advantage of their own structural information.