High-power diode lasers between 1.8μm and 3.0μm for military applications

Over the last years high-power diode lasers in the wavelength window between 1.8 mu m and 3.0 mu m have demonstrated impressive characteristics in terms of output power, beam quality and efficiency. This facilitates the realization of compact and efficient light sources for use in the field of infrared countermeasures (IRCM), optically pumped semiconductor lasers emitting in the 2-4 mu m regime, low probability of intercept communication links, and trace gas analysis. The small size of a diode laser chip of typically less than a square millimeter allows for the fabrication of compact scalable laser modules with output powers of up to 140W. We will present results on MBE grown (AlGaIn)(AsSb) quantum-well diode laser single emitters and bars emitting between 1.8 mu m and 3.0 mu m. Different epitaxial and resonator designs have been investigated in cw and pulsed mode in order to meet industrial needs of high wall-plug and fiber-coupling efficiencies. More than 30% maximum wall-plug efficiency in cw operation for single emitters and laser bars has been reached together with output powers for single emitters of 2W (cw) and 9W (pulsed). The single emitters and bars are all suitable for fiber coupling. For a 1-bar module typical coupling efficiencies between 70% and 80% have been established for 400 mu m core fibers. In terms of output power, an AuSn soldered laser stack built of 10x 20% fill factor bars emitting at 1908nm, results in a record value of 140W at 58A in cw condition.