title: Second-harmonic generation induced by electric currents in GaAs.
abstract: 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 pulses and demonstrate that it induces the same second-harmonic generation. In both cases, the induced second-order nonlinear susceptibility is proportional to the current density. This effect can be used for nondestructive, noninvasive, and ultrafast imaging of currents. These advantages are illustrated by the real-time observations of a coherent plasma oscillation and spatial resolution of current distribution in a device. This new effect also provides a mechanism for electrical control of the optical response of materials.
authors.affiliation: Department of Physics and Astronomy, The University of Kansas, Lawrence, Kansas 66045, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Ruzicka
authors.forename: Lalani K
authors.initials: LK
authors.lastname: Werake
authors.forename: Guowei
authors.initials: G
authors.lastname: Xu
authors.forename: Jacob B
authors.initials: JB
authors.lastname: Khurgin
authors.forename: E Ya
authors.initials: EY
authors.lastname: Sherman
authors.forename: Judy Z
authors.initials: JZ
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Zhao