Optical properties of quantum wells driven by a terahertz electric field

Summary form only given. A dc electric field oriented in the growth direction of a quantum well (QW) changes the optical absorption and thus enables electrically driven optical modulators. Though the electroabsorption change is intrinsically very fast mechanism (since it does not involve change in carrier density), the device operation speed is ultimately limited by its electronic components. To increase the operation speed, the modulation by a terahertz (THz) electric field, such as provided by a free-electron laser or table-top sources, can be used. Such a THz field tuned at resonance with the intersubband transitions can induce large changes in the interband optical absorption. Moreover, the modulation by a THz field gives rise to optical emission at frequencies that differ from the frequency of the incident optical field by an integer number of the THz frequencies. This nonlinear optical/THz photon mixing has potential application in frequency shifting devices.Recently, we studied the optical properties of a THz driven QW resolving several subbands, both in the conduction and valence bands, using the polarization semiconductor Bloch equations in the low density limit.