Terahertz radiation in semiconductor quantum dots driven by gigahertz waves: The role of tailoring the quasienergy spectrum

We explore the terahertz (THz) radiation from high-order harmonic fields in semiconductor quantum dots driven by gigahertz (GHz) waves, due to the availability of high power GHz sources. By mapping the optical problem to a transport problem, we are able to uncover several features in the THz wave generation processes. With the help of the Floquet theorem, the efficiency of THz wave generation, which is related to the particle transport, is determined by the bandwidth of the quasienergy spectrum. We not only reveal the interesting relation between optical processes and transport phenomena, but also find the optimal conditions (corresponding to resonances) and quench conditions (corresponding to band collapses) for THz wave generation. The nice on/off properties (the ratio of emission intensity at resonance to that at quench condition similar to 10(6)) are helpful for the design of THz source and have important applications in nanodevices with THz wave involved.