High-brightness 1040-nm tapered diode lasers

Semiconductor lasers with high beam quality and high optical output power are very attractive for a variety of applications such as optical pumping of solid-state lasers, fiber amplifiers and medical treatment. When easy and low-cost fabrication is a further requirement, devices based on tapered gain sections are the most promising candidates. Low modal gain, single quantum well InGaAs/A1GaAs devices emitting at 1040 nm were grown by molecular beam epitaxy. The lateral design consists of a tapered gain guided and a ridge-waveguide section having an overall length of mm. An output power of more than 11 W in qcw mode, lifetimes of more than 20,000 h and a record value for the beam quality factor M²of less than 1.5 up to a cw output power of 3.5 W are achieved resulting in an improved brightness of more than 255 MW/(cm²sr). In addition an external-cavity diode laser including a ridge-waveguide tapered amplifier structure is demonstrated to emit more than 2 W cw. The wavelength is tunable over a 60 nm range centered at 1020 nm. The beam quality parameter M² remains below 1.4 for output powers of 1 W over the whole range demonstrating the nearly diffraction limited behavior.