Efficient coupling of several broad area laser diodes into an optical fiber

A high brightness, fiber coupled optical pumping system is described based on readily available optical components. Operating at a wavelength of 670 nm we have achieved an output of 1.25 W from a 50 mu m core diameter fiber (0.22 NA) and 3.5 W from a 100 mu m core diameter fiber (0.22 NA). This represents a six- to eightfold increase over commercially available systems at that wavelength. The design is generic and can immediately be implemented at other wavelengths, where high brightness pumping systems are not commercially available. The design and implementation are detailed.