Terahertz harmonic generation from Bloch oscillating superlattices in quasi-optical arrays

We explored harmonic generation by Bloch oscillation in miniband superlattices driven by intense THz radiation from the UCSB free electron lasers, as a function of both THz intensity and applied DC bias. To accomplish this we integrated m m size superlattice mesas in a quasi-optical array which amplified a plane wave incident normal to the array and coupled it into the growth direction of the superlattice.; The superlattices studied consist of 50 periods of 80 A GaAs wells separated by 20 A Al.3Ga.7As barriers. The majority of the measurements were performed with a doping of 1016/cm 3.; We were able to successfully measure both second and third harmonic generation quantitatively. The harmonics are successfully modeled in terms of a quasi-classical picture of Bloch oscillation with semi-quantitative agreement.