Optical coherent control of electrical currents in semiconductor-metal hybrid nanostructures: physics and spectroscopic applications

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Phase-related optical beams have advanced the application of light in a broad variety of physical processes. Here, we study coherent control of ballistic electrical currents in hybrid semiconductor/metal nanodevices with phase-related ω/2ω near-infrared femtosecond pulse pairs. While such techniques are established in bulk semiconductors, the work of the first funding period has demonstrated their applicability to nanodevices. In particular, electrical currents as large as several μA are optically induced in single GaAs nanowires. Substantial evidence for an improved efficiency is found using optical antennas resonant for the ω pulse. While we have established optical antennas on bulk materials, we now will combine such structures with nanowires and nanotubes to demonstrate efficient deep sub-wavelength optical control of electrical currents. Such schemes will also permit to study current injection beyond the perturbative regime related to a third-order optical nonlinearity χ(3). It is expected that 5th order contributions will become relevant if not dominant under strong irradiance with ultrashort pulses. In parallel, we will work on novel spectroscopic applications of coherent control. In essence, quantum interference control of electrical currents is linear in the electric field of the 2ω light components. Such processes in combination with Fourier transform spectroscopy can conversely be utilized to retrieve phase and amplitude of the pulse itself. While proof-of-principle experiments have already been realized in the first funding period, we now want to nanoengineer detectors to realize ultrafast electric field oscilloscopes at optical frequencies. Taking full advantage of the phase-resolution of such schemes, we finally plan to demonstrate experiments on transient optical nonlinearities with amplitude-, phase, and time-resolution.