Stimulated emission in InAs/InGaSb/InAs/AlSb type-II quantum- well (QW) lasers was observed up to room temperature at 4.5 micrometer, optically pumped by a pulsed 2-micrometer Tm:YAG laser. The absorbed threshold peak pump intensity was only 1.1 kW/cm2 at 300 K, with a characteristic temperature T0 of 61.6 K for temperatures up to 300 K. We have also studied another type-II QW laser using 0.808-micrometer pumping sources with a much longer pulse length of 50 microseconds. The devices demonstrated a maximum output power of 1.6 W per facet at 83 K, with a corresponding differential external quantum efficiency of 24.8%.
This paper will summarize our research in mid-infrared semiconductor lasers, focusing mainly on the GaInAsSb/AlGaAsSb material system. The technical problems that must be solved to achieve efficient operation of long-wavelength semiconductor lasers will then be outlined. Finally, options for using near- term lasers at lower temperatures will be considered.
Continuous-wave GaAs/GaAlAs edge-emitting diode lasers were used to pump GaAs/AlGaAs and InGaAs/AlGaAs vertical cavity surface-emitting lasers (VCSELs) with resonant periodic gain (RPG) at room temperature. Pump threshold as low as 11 mW, output powers as high as 27 mW at 850 nm, and external differential quantum efficiencies of about 70 percent were observed in GaAs/AlGaAs surface -emitters; spectral brightness 22 times that of the pump laser was also observed. Output powers as high as 85 mW at 950 nm and differential quantum efficiencies of up to 58 percent were recorded for the InGaAs surface-emitting laser. This is the highest quasi-CW output power ever reported for any RPG VCSEL, and the first time such a device has been pumped using an injection laser diode.