Toward a semiconductor-based terahertz nonlinear medium

The recent growth of interest in the terahertz (THz) region of the spectrum has spurred the development of new THz elements in analogy to elements used in optical and microwave systems. Nonlinear as well as linear elements are needed. In this study we explore theoretically the use of valence-subband nonparabolicity in strained p-type quantum wells (QWs) for third-harmonic generation. All fields—the fundamental as well as the harmonic—are polarized in the quantum-well plane, thus facilitating integration with lateral high-frequency electronic devices as well as for coupling to free-space fields. For strained InAs quantum wells, we find that the corresponding value of χ(3) can be as large as View the MathML source. The predicted values of χ(3), though not extremely large, are nevertheless in the range of those associated with intersubband transitions in the mid-infrared region of the spectrum.