A novel design-friendly device called the transistor-injected dual doping quantum cascade laser (TI-D2QCL) with two different doping in each stack of a homogeneous superlattice is proposed. By adjusting the base-emitter bias Vbe of the bipolar transistor to supply electrons in the dual doping regions, charge quasi-neutrality can be achieved to generate different optical transitions in each cascading superlattice stack. These transitions are then stacked and amplified to contribute to a broad flat gain spectrum. Model calculations of a designed TI- D2QCL show that a broad flat gain spectrum ranging from 9.41um to 12.01um with a relative bandwidth of 0.24 can be obtained, indicating that the TI- D2QCL with dual doping pattern may open a new pathway to the appealing applications in both MIR and THz frequency ranges, from wideband optical generations to advanced frequency comb technologies.
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