Extra bright high power laser bars

We present improvements of the lateral beam divergence and brightness of gain-guided mini-bars for emission at 976nm at highest brightness levels. The beam characteristics of devices in production are tailored for optimized fiber coupling to fiber diameter 200μm and numerical aperture 0.22, corresponding to a beam parameter product of 22 mm mrad. Cost-efficient coupling to this fiber requires a beam parameter product tailored to 15 mm mrad in lateral direction. The corresponding devices feature 5 emitters with cavity length 4mm and a lateral electrical contact width of 100μm per emitter. These bars can be driven to 44W before exceeding the beam parameter product of 15 mm mrad, corresponding to a slow axis beam divergence of 7° and a linear brightness of 2.9 W/mm mrad. In this work, we demonstrate results of two new mini-bar designs. The first design is intended for cost-reduction of divergence limited coupling systems and improves the output power at the slow axis divergence limit of 7° from 44W to 52W. The second structure, designed for coupling to fibers with beam parameter products as low as 11 mm mrad, exhibits significantly higher beam quality and excellent maximum linear brightness of 4.5 W/mm mrad, albeit at lower output power. All the structures exhibit power conversion efficiencies approaching 70%.