5.0 μm emitting interband cascade lasers with superlattice and bulk AlGaAsSb claddings

We present a comparison between interband cascade lasers (ICLs) with a six-stage active region emitting at 5 μm with AlSb/InAs superlattice claddings and with bulk $A l 0.85 G a 0.15 A s 0.07 S b 0.93$ claddings. Utilizing bulk AlGaAsSb claddings with their lower refractive index compared to the more commonly used AlSb/InAs superlattice claddings, the mode-confinement in the active region increases by 14.4% resulting in an improvement of the lasing threshold current density. For broad area laser and under pulsed excitation, the ICL with AlGaAsSb claddings shows a lower threshold current density of $J t h=396 A/ c m 2$ compared to $J t h=521 A/ c m 2$ of the ICL with superlattice claddings. Additionally, a higher characteristic temperature was obtained for the ICL with bulk claddings. Emission in pulsed operation is observed up to 65 °C.