Spin-dependent terahertz nonlinearities at inter-valence-band absorption in p-Ge

Far-infrared absorption and photon drag effect have been investigated in p- type germanium as a function of intensity of a high-power pulsed far-infrar ed molecular laser. Optical transmission shows saturation independent of th e state of polarization of the radiation whereas in the photon drag effect a pronounced linear-circular dichroism occurs. Linear-circular dichroism is caused by spin-selective excitations as a result of selection rules and, e qually important, multiphoton transitions with a rate comparable to one-pho ton absorption. (C) 1999 Elsevier Science B.V. All rights reserved.