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 $1.55\ensuremath{\mu}\mathrm{m}$. Electrical currents generated in low-temperature-grown (LT) and normal bulk GaAs are collected via gold electrodes. Current densities as high as $3\mathrm{nA}/\ensuremath{\mu}{\mathrm{m}}^{2}$ in LT-GaAs are measured for injected carrier densities as low as ${10}^{14}{\mathrm{cm}}^{\ensuremath{-}3}$ and for peak irradiances of $18\mathrm{MW}{\mathrm{cm}}^{\ensuremath{-}2}$ ( $1.550\ensuremath{\mu}\mathrm{m}$) and $3\mathrm{kW}{\mathrm{cm}}^{\ensuremath{-}2}$ ( $0.775\ensuremath{\mu}\mathrm{m}$).