Multi-frequency THz emission from asymmetric GaAs/AlGaAs quantum well patterned by intermixing

The effect of intermixing on the THz generation is studied on a quantum well structure excited by a femtosecond pulse laser. An asymmetric coupled GaAs/AlGaAs quantum well is used to enhance the nonlinear effect for THz generation. Our theoretical results indicate that the energy separation between two sublevels, i.e. the frequency of the generated THz radiation, increases with diffusion of the Al component. Then the intensity of the THz emission decreases with diffusion length due to the reduction of nonlinear effect in the quantum well. The intermixing also controls the field at the anticrossing resonance of the two sublevels, at which the THz radiation efficiency will be strongly enhanced. Due to our special design, the resonant field is fixed in the intermixing process. Based on these results, a multi-frequency quantum well chip with emission from 2 to 9 THz may be fabricated by using the technique of selective intermixing.