Study of the mechanism of “smile” in high power diode laser arrays and strategies in improving near-field linearity

High power diode lasers have found increased applications in pumping of solid state or fiber laser systems for industrial, military and medical applications as well as direct material processing applications. The non-linearity of the near-field of emitters (or the so called ldquosmilerdquo effect) in a laser diode array poses significant challenges in optical coupling and beam shaping and has become one of the major roadblocks in broader applications of laser arrays. Increasing the near-field linearity of a pumping laser diode array enables the laser system manufacturer to improve the laser system compactness, optical coupling efficiency, power, and beam quality while at the same time reducing manufacture cost in the laser system. Therefore, the near-field linearity of a laser bar is one of the key specifications of laser array products and improving the near field performance is especially important in order to increase production yield, reduce cost and gain competitiveness. In this paper, we will study the mechanism of ldquosmilerdquo in high power diode laser arrays and discuss the strategies and ways to achieve low ldquosmilerdquo.