Electrically pumped tunable terahertz emitter based on intersubband transition

An electrically pumped three-level system was designed and fabricated using an AlGaAs/GaAs multiple quantum well structure. Under appropriate biases, the structure emits terahertz (THz) radiation, as a result of diagonal (or interwell) intersubband transition. The emission spectra were resolved using an external Fourier transform infrared spectrometer. The center frequency of the emission was voltage tunable. The emission spectra and the power-voltage relation showed clear evidence that the middle level was depopulated by fast longitudinal optical-phonon scattering, thus, a population inversion between the two upper levels is feasible.