High-brightness emission from stripe-array broad area diode lasers operated in off-axis external cavities

Abstract

Phase-coupled stripe-array diode lasers show a strong double-lobed far-field because adjacent stripes tend to operate in the anti-phase supermode. One way to achieve a stable phase relationship and global coupling of the emitters of such a stripe-array is off-axis feedback. In this work several off-axis external cavity designs are discussed. A 400 孠wide emitter stripe array consisting of 40 stripes with a pitch of 10 孠was investigated. By operating this device in a Littrow type off-axis external cavity, more than 2 W of output power of near diffraction-limited, single longitudinal mode emission with a brightness as high as 87MW/cm⭳tr could be achieved. The technique of off-axis feedback was also adapted to realize spectral beam combining of 25 emitters of a laser bar. The experimental data are compared with numerical simulations using a new theoretical model including feedback.