Diode laser arrays for 1.8 to 2.3 μm wavelength range

Abstract

High-power diode lasers in the mid-infrared wavelength range between 1.8μm and 2.3μm have emerged new possibilities either for direct military applications or as efficient pump sources for laser sources in the 2-4μm wavelength range for infrared countermeasures. GaSb based diode lasers are naturally predestinated for this wavelength range and offer clear advantages in comparison to InP based diode lasers in terms of output power and wall-plug efficiency. We will present results on different MBE grown (AlGaIn)(AsSb) quantum-well diode laser single emitters and linear laser arrays, the latter consisting of 19 emitters on a 1cm long bar, emitting at different wavelengths between 1.8μm and 2.3μm. Single emitters have resonator lengths between 1.0 and 1.5mm and stripe widths between 90μm and 200μm. Laser bars with 20% and 30% fill factors have been processed. For single emitters the electro-optical behaviour, beam quality and wavelength tunability have been investigated in detail. For diode laser bars mounted either on actively or passively cooled heat sinks by Indium or AuSn solder, more than 20W at 1.9μm in continuous-wave mode have been achieved at a heat sink temperature of 20°C resulting in maximum wall-plug efficiencies of 30%. Even at 2.2μm more than 16W have been measured, impressively demonstrating the potential of GaSb based diode lasers well beyond wavelengths of 2μm. Application driven fiber coupled single emitter based modules with 600mW as well as fiber coupled bar based modules with 20W have been realized.