HIGH-INTENSITY RECTANGULAR FIBER-COUPLED DIODE-LASER ARRAY FOR SOLID-STATE LASER PUMPING

A high-power diode laser bar coupling scheme with rectangular optical fibers is proposed, and the concept is tested on a scale version: an individual diode laser array and a single rectangular fiber. 60% of the power from a 1-W cw, 213-mum-wide 20-stripe diode array is coupled into a 216 mum x 28 mum 0.66 numerical aperture optical fiber, which produces intensities at the fiber output face of 9.9 kW cm-2. The elliptical, dual-lobed far-field intensity pattern of the diode laser output, with divergence of 39-degrees x 13-degrees FWHM is converted on passing through the fiber into a single-lobed, nearly circular pattern with a FWHM divergence of 21-degrees x 22-degrees. The beam quality is reduced by only a factor of 30 when this coupling method is used. Alignment tolerances in the three planes of movement are measured and found to be in excess of 10 mum.