Imposing narrow spectral bandwidth in a system of passively combined fiber lasers

We investigate intra-cavity coherent beam combining in a system of two fiber lasers when a spectrally selective element is inserted in one of the lasers. We found that narrow spectral content can be imposed on the other laser, resulting in narrowband operation of the system with high combining efficiency. Furthermore, the combining efficiency decreases as the imposed wavelength is farther away from the natural lasing wavelength of the system and depends on the gain imbalance between the lasers. Our results demonstrate, for the first time, the rich dynamics associated with the spectral mode competition in the intra-cavity coherently combined system.