Submillimeter quantum cascade laser in the GaAs/AlGaAs system

We propose to develop a submillimeter quantum cascade laser in the GaAs/AlGaAs material system. This device relies on intersubband transitions in GaAs quantum wells of the device for lasing. Preliminary calculations show that there is sufficient gain to produce lasing in the wavelength range 80 to 125 mu m. The active region of the laser structure consists of coupled quantum wells which can be grown by molecular beam epitaxy (MBE). The model uses a 30 nm-wide active quantum well which contains two levels separated by 14.8meV which corresponds to a wavelength of 83.5 mu m at a bias of 8850V/cm with 12.2 nm and 29.8 nm wide quantum well energy filters inserted on either side of the active well. The energy filters are designed to allow only electrons with the energy of the upper state to be injected into the active well and only electrons with the energy of the lower state to be extracted fi-om the active well. The proposed device uses a 10-period injector/active well/collector structure. The collector/injector is a superlattice region, which acts as a reservoir for the electrons. The gain of this system has been calculated to be approximately 2500 cm(-1). Threshold current density has been calculated to be about 622A/cm(2) at 77K.