Highly reliable 75W InGaAs/AlGaAs laser bars with over 70% conversion efficiency

Diode lasers with a high very conversion efficiency can be obtained when carefully taken into account several partly opposed requirements for the design of the layer structure. Results are given for 940nm laser structures based on the well established InGaAs/AlGaAs material with a relatively low vertical divergence of about 45° including 95% of optical power. Laser bars were processed and mounted on passively cooled heat sinks. 73% conversion efficiency was achieved at 70W output power. 150μm stripe lasers with only 1500μm resonator length mounted on usual C-mounts have a thermal rollover of about 18W, which is a record high value for a resonator length below 2mm. Reliability tests show an excellent stability at 75W in CW and 95W in long pulse operation mode over about 10000h test time.