Brilliant low-fill-factor diode laser bars at 9xx nm for fiber coupling

Abstract

New semiconductor multi emitters combine the advantages of laser bars and strength of single emitters for fiber coupling applications. We introduce a new technology to drive the device at highest power density at the laser facet. The new technology enables us to reduce the fill factor while maintaining output power per laser bar at reliable and efficient operation. The overall output power and slow axis beam parameter product is scaled with the numbers of emitters and may be coupled into a single fiber with low effort in beam shaping or fiber combining. We demonstrate that multi emitters can operate at same power level as the same number of single emitters. In this paper we present data on highly efficient and reliable 9xx nm laser bars designed for a defined fiber diameter and numerical aperture. For comparison single emitters and short bars with different fill factors were investigated. Efficiencies above 60% were reached with 4mm cavity length and fast axis far field angles of 45° (95%). Stable operation at powers up to 70W from short bars with five 100μm wide emitters was reached. Slow axis divergence is below 7° up to power levels of 38W and is suitable for coupling into 200μm NA 0.22 fibers with only slow axis and fast axis collimation without beam rearrangement.