Brian A. Ruzicka

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We demonstrate a new, nonlinear optical effect of electric currents. First, a steady current is generated by applying a voltage on a doped GaAs crystal. We demonstrate that this current induces second-harmonic generation of a probe laser pulse. Second, we optically inject a transient current in an undoped GaAs crystal by using a pair of ultrafast laser(More)
Atomically thin molybdenum disulfide is emerging as a new nanomaterial with potential applications in the fields of electronic and photonics. Charge carrier dynamics plays an essential role in determining its electronic and optical properties. We report spatially and temporally resolved pump-probe studies of charge carriers in atomically thin molybdenum(More)
Nardeep Kumar,1 Brian A. Ruzicka,1 N. P. Butch,2 P. Syers,2 K. Kirshenbaum,2 J. Paglione,2 and Hui Zhao1,* 1Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA 2Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA (Received 1 April 2011; revised(More)
We report observation of intrinsic inverse spin Hall effect in undoped GaAs multiple quantum wells with a sample temperature of 10 K. A transient ballistic pure spin current is injected by a pair of laser pulses through quantum interference. By time resolving the dynamics of the pure spin current, the momentum relaxation time is deduced, which sets the(More)
Spatiotemporal dynamics of excitons in isolated semiconducting single-walled carbon nanotubes are studied using transient absorption microscopy. Differential reflection and transmission of an 810-nm probe pulse after excitation by a 750-nm pump pulse are measured. We observe a biexponentially decaying signal with a fast time constant of 0.66 ps and a slower(More)
The energy relaxation of carriers in reduced graphene oxide thin films is studied using optical pump-probe spectroscopy with two probes of different colors. We measure the time difference between peaks of the carrier density at each probing energy by measuring a time-resolved differential transmission and find that the carrier density at the lower probing(More)
Subpicosecond ac spin-current pulses are generated optically in GaAs bulk and quantum wells at room temperature and at 90 K through quantum interference between one-photon and two-photon absorptions driven by two phase-locked ultrafast laser pulses that are both circularly polarized. The dynamics of the current pulses are detected optically by monitoring,(More)
There is a growing interest in the earth abundant and nontoxic iron disulfide (FeS(2)) photovoltaic materials. Here, we report the synthesis of FeS(2) nanoplates with different spectral features which we have associated with thicknesses and crystallization. The structure and crystalline order of ultrathin FeS(2) nanoplates have a strong influence on the(More)
Eric J. Loren, Brian A. Ruzicka, Lalani K. Werake, Hui Zhao, Henry M. van Driel, and Arthur L. Smirl Laboratory for Photonics and Quantum Electronics, 138 IATL, University of Iowa, Iowa City, Iowa 52242,USA Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA Department of Physics and Institute for Optical Sciences,(More)