Spatial Filtering Properties of Large-Mode-Area Fibers with Confined Gain Dopants
Frontiers in Optics 2009/Laser Science XXV/Fall 2009 OSA Optics & Photonics Technical Digest
Fiber-laser output power (W) Confined-gain laser C o n v e n t i o n a l l a s e r Averaged measured M 2 E18306 • Richard Roides and Zhuo Jiang • Modeling work funded by: • Experimental work funded by: • Fibers provided by: Confining the gain to the center of the fiber core provides an exceptional degree of spatial filtering E18307 • The beam quality in conventional fiber lasers and amplifiers degrades with increasing pump power due to transverse spatial hole burning • Proper radial tailoring
... radial tailoring of the gain-doping profile can provide spatial filtering of the higher-order modes without introducing any loss -reducing the diameter of the gain-doping profile with respect to the waveguide diameter results in highest gain for the fundamental mode, regardless of saturation level • The beam quality in confined-gain-dopant fiber lasers and amplifiers is good and constant at all pumping levels • This gain-filtering concept is power/energy scalable and robust with respect to seed purity, core diameter, and numerical aperture Summary Confining the gain for modal filtering has been used for decades E18309 • Solid-state lasers: -D. L. Sipes, "Highly efficient neodymium: yttrium aluminum garnet laser end pumped by a semiconductor laser array," Appl. Phys. Lett. 47, 74 (1985). , "High-power (>10 W) continuous-wave operation from 100-nm-aperture 0.97-nm-emitting Al-free diode lasers," Appl. -energy single-transverse-mode Q-switched fiber laser based on a multimode large-mode-area erbium-doped fiber," Opt. Lett. 23, 1683 (1998).