Magnetic-field-induced fourfold azimuthal angle dependence in the terahertz radiation power of (100)InAs

The azimuthal angle dependence in the terahertz radiation power of (100) InAs under 1 T magnetic field is presented. Results show that although the dominant radiation mechanism is surge current, azimuthal-angle-dependent radiation due to the nonlinear effect is also observed. The twofold symmetry of the p-polarized terahertz radiation power was modified to a fourfold symmetry with the transverse magnetic field. Moreover, results exhibited fourfold symmetry for the s-polarized terahertz power even with no applied field. The anisotropic intervalley scattering of photocarriers is tentatively proposed as the origin of quadrupole response and the fourfold emission symmetry. (c) 2007 American Institute of Physics.