title: Large four-wave mixing of spatially extended excitonic states in thin GaAs layers.
abstract: We study the size dependence of the nonlinear response of weakly confined excitons for the size region beyond the long wavelength approximation regime. The observed degenerate-four-wave mixing signal of GaAs thin layers exhibits an anomalous size dependence, where the signal is resonantly enhanced at a particular thickness region. The theoretical analysis elucidates that this enhancement is due to the size-resonant enhancement of the internal field with a spatial structure relevant to the nondipole-type excitonic state. These results establish the formerly proposed new type of size dependence of nonlinear response due to the nonlocality induced double resonance.
authors.affiliation: Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan. ishi@mp.es.osaka-u.ac.jp
authors.forename: Hajime
authors.initials: H
authors.lastname: Ishihara
authors.forename: Kikuo
authors.initials: K
authors.lastname: Cho
authors.forename: Koichi
authors.initials: K
authors.lastname: Akiyama
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tomita
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Nomura
authors.forename: Toshiro
authors.initials: T
authors.lastname: Isu