10 W high-efficiency high-brightness tapered diode lasers at 976 nm

Tapered diode lasers combine high output power and a beam quality near to the diffraction limit resulting in very high brightness. Therefore, they are finding use in a wide range of applications today, such as pumping of rare-earth-doped fibre amplifiers, tunable frequency doubling of diode lasers for blue-green outputs, and non linear spectroscopy. Due to increasing brightness and lifetime tapered lasers even become attractive for material processing and for telecom applications like pumping of Er-doped fiber amplifiers or raman amplifiers. In order to further enhance the brightness of tapered diode lasers the output power has to be increased while simultaneously the beam quality has to be kept near the diffraction limit. For this purpose we have grown low modal gain, single quantum well InGaAs/AlGaAs devices emitting at 976 nm by molecular beam epitaxy. The lateral design of the investigated laser diodes consists of a tapered section and a ridge-waveguide section. Since it has been shown by previous simulations and experiments that longer tapered sections allow higher output power with unchanged beam quality, we use tapered section lengths of 2000 μm, 3000 μm and 4000 μm. The beam quality parameter M² and output powers as well as the nearfields of the different structures were carefully investigated. For longer devices we reach an optical output power of more than 10 W per single emitter in continuous wave mode (cw) without any distinct thermal rollover.