Quantum interference control of currents in CdSe with a single optical beam

We show that ballistic current generation can occur in a semiconductor via quantum interference between absorption pathways for orthogonal polarizatio n components of a single-frequency beam. This effect occurs for a subset of noncentrosymmetric materials, is macroscopically associated with a second- order nonlinear optical susceptibility, and produces current injection line arly proportional to the beam intensity. We demonstrate this in wurtzite Cd Se (E-g=1.75 eV) at 295 K using cw and femtosecond optical sources of wavel ength 600-750 nm (2.07-1.66 eV). The intensity and spectral dependence are in reasonable agreement with a first-principles calculation. Continuous cur rent density of 30 mu A cm(-2) is produced for 60 mW cm(-2) intensity at 63 3 nm. (C) 1999 American Institute of Physics. [S0003-6951(99)00843-8].