Narrow-linewidth, high-brightness laser diode arrays

High-brightness, high-power diode laser arrays are expanding their role in pumping multilevel solid-state laser systems. Various advanced solid-state laser systems take advantage of strong but narrow absorption lines and thus, demand a very small linewidth of the pump source. Conventional diode laser bars cover only the lower part of required brightness range and have typically a broad emission spectrum. In this work, we describe a laser diode array source consisting of broad area laser diodes utilizing an angled-grating distributed feedback (/spl alpha/-DFB) structure operating at a wavelength of 960.5 nm, which is an absorption line for Er:YAG solid-state material lasing near 3 /spl mu/m. Because the gain for this laser transition is quite low, the performance is strongly dependent upon the spectral and spatial quality of the pump beam. In order to obtain adequate power from the laser, a pump source is required which could deliver several watts of power into a 50 /spl mu/m spot within less than 0.3 NA with a spectral bandwidth of <1 nm at precisely 960.5 nm.