High-brightness fiber-coupled pump sources at 88X nm and 79X nm

Developments in Nd-based lasers pumped on the 4 I 9/2 → 4 F 3/2 transition have led to demands for increased power, brightness, and spectral stability from diode pump sources. We describe the development of fiber coupled diode pump sources that generate >120W of power from a 400μm, 0.22NA fiber at 88Xnm wavelengths. In order to maintain spectral purity at these high powers, we investigated the use of Volume Bragg Gratings to stabilize the wavelength of these multi-bar systems. A detailed study of the trade-offs between facet reflectivity and VBG reflectivity was conducted in order to determine an optimal combination that balances output power and locking range. In complement to the developments in 88Xnm pumping, recent interest in eye-safe fiber lasers have resulted in the development of Tm-doped fiber lasers pumped at 79X wavelengths. We describe the development of fiber coupled products with >80W from a 200μm, 0.22NA fiber, including the use of optimized bar geometries to improve fiber coupling efficiency.