Passive coherent locking of fiber lasers using volume Bragg gratings

We introduce a novel technique of coherently locking fiber lasers using volume Bragg gratings (VBGs) recorded in photo-thermo-refractive (PTR) glass as a passive multiplexer between channels. A two-channel coherently-locked Ybdoped fiber laser system with a narrow linewidth (~2.5 pm) and linear polarization (PER >20 dB) is demonstrated at a level of ~ 4 W (limited by pump). Scaling of this technique to coherently lock multiple (>2) fiber laser channels is discussed.