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InAs-Based Interband-Cascade-Lasers in the 6-7 µm Wavelength Range

Interband-Cascade-Lasers (ICLs) have emerged as efficient and reliable laser sources over a broad wavelength range in the mid-infrared spectral region. Here they meet the demand from several applications such as high sensitivity tunable laser absorption spectroscopy (TLAS). For ICLs grown on GaSb substrates, continuous wave operation at room temperature has already been demonstrated up to wavelengths of 5.6 μm. For longer wavelength devices, the low thermal conductivity and the demanding growth of the superlattice cladding become increasingly challenging, as thicker claddings are required to avoid optical leakage into the substrate. ICLs grown on InAs-substrates circumvent these challenges by replacing the superlattice cladding with a highly doped InAs-layer. As the plasmon frequency of this material comes in range of the emission wavelength, the refractive index is significantly reduced and enables mode confinement within the undoped InAs waveguide layers. Emission wavelengths up to 10.4 μm have been demonstrated for these ICL types at cryogenic temperatures.