Since distributed feedback interband cascade lasers have already shown to be able to cover a wide window in the mid infrared region (2.8 µm  to 5.2 µm ) they are suitable light sources for applications where smallest concentrations of several gases have to be traced via absorption spectroscopy. With their broken gap alignment of the two binaries GaSb and InAs, carriers re-enter the conduction band after making a radiative recombination. This enables multiple quantum well stages in a stacked scheme as in quantum cascade lasers. Due to the interband nature of the transition, the gain per stage is larger and fewer stages are required to reach lasing threshold at moderate current levels. With threshold currents in the ten milliampere range, operation voltages below ten volts and output power of a few milliwatts, the interband cascade laser are best suited for spectroscopic applications. We demonstrate an array of multiple spectrally monomode emitters on a single semiconductor chip. The targeted emission wavelengths cover the mid infrared regime from around 3.3 to 3.5 microns.
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