Comparison between InAs-based and GaSb-based Interband cascade lasers with hybrid superlattice plasmon-enhanced claddings

We compare InAs-based and GaSb-based interband cascade lasers (ICLs) with the same 12 stages active region designed to emit at a wavelength of 4.6 {\mu}m. They employ a hybrid cladding architecture with the same geometry and inner claddings consisting of InAs/AlSb superlattices but different outer claddings: The InAs-based ICL employs plasmon enhanced n-type doped InAs layers while the GaSb-based ICL employs plasmon-enhanced n-type doped InAs_0.915 Sb_0.085 claddings lattice matched to GaSb. Due to the lower refractive index of n+-InAsSb (n=2.88) compared to n+-InAs (n=3.10) and higher refractive index of separate confinement layers, the GaSb-based ICL shows a 3.8 % higher optical mode confinement in the active region compared to the InAs-based ICL. Experimentally, the GaSb-based ICL shows a 17.3 % lower threshold current density in pulsed operation at room temperature. Also presented is the influence of geometry and doping variation on confinement factors and calculated free carrier absorption losses in the GaSb-based ICL.