Quantum cascade lasers in the 8-9 μm wavelength region

We have recently demonstrated intersubband unipolar lasers in the wavelength region between 4.2 and 4.6 μm. In these devices light is generated by electronic transitions between conduction band subbands arising from size quantization in quantum wells. The emission wavelength is therefore controlled by the layer thicknesses and can be tailored in a wide spectral range using the same heterostructure material. We substantiate this claim and report QC lasers operating at more than twice the wavelength of the previous ones, proving that the same design criteria can be indeed extended to fabricate semiconductor lasers where the lasing transition is independent upon the material band gap