Comprehensive analysis of the internal losses in 2.0 µm (AlGaIn)(AsSb) quantum-well diode lasers

We have fabricated and characterized high-power 2.0 µm-wavelength (AlGaIn)(AsSb) quantum-well diode lasers emitting a power of 1.7 W in continuous-wave operation and over 9 W in pulsed operation at 300 K heat sink temperature. For potential further improvement of laser performance, the different contribution to the internal losses alpha(ind i) has been analyzed in detail for the present laser structure. Consistent results have been obtained for a series of samples, for which different design parameters were varied systematically: As expected, the losses in the cladding layers are dominated by fee carrier absorption in the p-doped cladding. The cross section for free-hole absorption in Al(0.84)Ga(0.16)As(0.06)Sb(0.94) is determined to Sigma(ind P)= 4.6x10(exp -17) cm2, which is comparable to values reported in the literature for (AlGaIn)(AsP)-based lasers emitting at 1.5 µm. The losses in the active region were found to increase linearly with increasing number of quantum wells at a rate of 1.5 cm-1 per quantum well, whereas the losses in the separate confinement layers are negligible.