Observation of coherently controlled photocurrent in unbiased, bulk GaAs

We demonstrate room temperature coherent generation and control of a directional photocurrent in bulk GaAs via simultaneous one- and two-photon interband absorption processes using phase-related 1 ps or 175 fs pulses at 0.775 and 1.55 mu m. Electrical currents generated in low-temperature-grown (LT) and normal bulk GaAs are collected via gold electrodes. Current densities as high as 3 nA/mu m(2) in LT-GaAs are measured for injected carrier densities as low as 10(14) cm(-3) and for peak irradiances of 18 MW cm(-2) (1.550 mu m) and 3 kW cm(-2) (0.775 mu m).