title: Direct measurements of multi-photon induced nonlinear lattice dynamics in semiconductors via time-resolved x-ray scattering.
abstract: Nonlinear optical phenomena in semiconductors present several fundamental problems in modern optics that are of great importance for the development of optoelectronic devices. In particular, the details of photo-induced lattice dynamics at early time-scales prior to carrier recombination remain poorly understood. We demonstrate the first integrated measurements of both optical and structural, material-dependent quantities while also inferring the bulk impulsive strain profile by using high spatial-resolution time-resolved x-ray scattering (TRXS) on bulk crystalline gallium arsenide. Our findings reveal distinctive laser-fluence dependent crystal lattice responses, which are not described by previous TRXS experiments or models. The initial linear expansion of the crystal upon laser excitation stagnates at a laser fluence corresponding to the saturation of the free carrier density before resuming expansion in a third regime at higher fluences where two-photon absorption becomes dominant. Our interpretations of the lattice dynamics as nonlinear optical effects are confirmed by numerical simulations and by additional measurements in an n-type semiconductor that allows higher-order nonlinear optical processes to be directly observed as modulations of x-ray diffraction lineshapes.
authors.affiliation: Department of Physics, DePaul University, Chicago, Illinois 60614, USA.|Lawrence Livermore National Laboratory, Livermore, California 94550-9234, USA.
authors.forename: G Jackson
authors.initials: GJ
authors.lastname: Williams
authors.affiliation: Frontier in Extreme Physics, Korea Research Institute of Standards and Science (KRISS), Daejeon 305-340, Republic of Korea.|Department of Nanoscience, University of Science and Technology (UST), Daejeon 305-350, Republic of Korea.
authors.forename: Sooheyong
authors.initials: S
authors.lastname: Lee
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Donald A
authors.initials: DA
authors.lastname: Walko
authors.affiliation: Department of Physics, DePaul University, Chicago, Illinois 60614, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Watson
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94550-9234, USA.|Department of Physics, Soong-Sil Univeristy, Seoul 06978, Republic of Korea.
authors.forename: Wonhuyk
authors.initials: W
authors.lastname: Jo
authors.affiliation: Department of Physics, Soong-Sil Univeristy, Seoul 06978, Republic of Korea.
authors.forename: Dong Ryeol
authors.initials: DR
authors.lastname: Lee
authors.affiliation: Department of Physics, DePaul University, Chicago, Illinois 60614, USA.
authors.forename: Eric C
authors.initials: EC
authors.lastname: Landahl