Diffraction limited 3.15 μm cascade diode lasers

In this work we report on design and development of the single spatial mode cascade diode lasers operating near 3.15 μm. The narrow ridge lasers generated more than 40 mW of continuous wave (CW) power at room temperature (RT) in diffraction limited beam. Each gains stage consists of three nominally 1.3%-compressively-strained Ga
₄₅
In
₅₅
As
₃₀
Sb
₇₀
quantum wells (QWs), spaced by 50 nm of quinary AlGaInAsSb barriers, and sandwiched between two 200-/250-nm-wide barrier layers of the same composition. The tunnel junction/carrier injector heterostructure was based on 100-μm-thick AlGaAsSb graded layer, 10-nm-thick GaSb layer and moderately doped 25-nm-wide chirped AlSb/InAs superlattice.